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Alternative Fuels Data Center: Alternative Fuels and Advanced Vehicles

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More than a dozen alternative fuels are in production or under development for use in alternative fuel vehicles and advanced technology vehicles. Government and private-sector vehicle fleets are the primary users for most of these fuels and vehicles, but individual consumers are increasingly interested in them.

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Alternative Fuels Data Center: Alternative Fuels and Advanced Vehicles

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More than a dozen alternative fuels are in production or under development for use in alternative fuel vehicles and advanced technology vehicles. Government and private-sector vehicle fleets are the primary users for most of these fuels and vehicles, but individual consumers are increasingly interested in them.

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Alternative Fuels Data Center: Alternative Fuels and Advanced Vehicles

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More than a dozen alternative fuels are in production or under development for use in alternative fuel vehicles and advanced technology vehicles. Government and private-sector vehicle fleets are the primary users for most of these fuels and vehicles, but individual consumers are increasingly interested in them.

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Diesel engines are more fuel-efficient and have more low-end torque than similar-sized gasoline engines, and diesel fuel contains roughly 10% to 15% more energy than gasoline. So, diesel vehicles can often go about 20% to 35% farther on a gallon of fuel than their gasoline counterparts. Plus, today's diesel vehicles are much improved over diesels of the past.

Better Performance

Improved fuel injection and electronic engine control technologies have

Increased power

Improved acceleration

Increased efficiency

New engine designs, along with noise- and vibration-damping technologies, have made them quieter and smoother. Cold-weather starting has been improved also.

Cleaner

Today's diesels must meet the same emissions standards as gasoline vehicles. Advances in engine technologies, ultra-low sulfur diesel fuel, and improved exhaust treatment have made this possible.

Although emissions of particulates and smog-forming nitrogen oxides (NOx) are still relatively high, new "clean" diesel fuels, such as ultra-low sulfur diesel and biodiesel, and advances in emission control technologies will reduce these pollutants also.

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Diesel engines are more fuel-efficient and have more low-end torque than similar-sized gasoline engines, and diesel fuel contains roughly 10% to 15% more energy than gasoline. So, diesel vehicles can often go about 20% to 35% farther on a gallon of fuel than their gasoline counterparts.

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Ethanol is a renewable, domestically produced alcohol fuel made from plant material, such as corn, sugar cane, or grasses. Using ethanol can reduce oil dependence and greenhouse gas (GHG) emissions. Ethanol fuel use in the U.S. has increased dramatically from about 1.7 billion gallons in 2001 to about 12.6 billion in 2020. ¹

E10 and E15

E10 and E15 are blends of ethanol and gasoline. The number after the "E" indicates the percentage of ethanol by volume.

Most of the gasoline sold in the U.S. contains up to 10% ethanol-the amount varies by region. All automakers approve blends up to E10 in their gasoline vehicles.

As of 2011, EPA began allowing the use of E15 in model year 2001 and newer gasoline vehicles. ² Pumps dispensing E15 must be labeled (see example). A vehicle's owner manual may indicate the maximum ethanol content recommended for it by the automaker.

Ethanol contains about one-third less energy than gasoline. So, vehicles will typically go 3% to 4% fewer miles per gallon on E10 and 4% to 5% fewer on E15 than on 100% gasoline. ³

E85 (Flex Fuel)

E85, also called flex fuel, is an ethanol-gasoline blend containing 51% to 83% ethanol, depending on geography and season. Summer blends tend to have more ethanol while winter blends have less. ⁴ E85 can be used in FFVs, which are specially designed to run on gasoline, E85, or any mixture of the two. FFVs are offered by several automakers. We provide a brief guide to help you determine if your vehicle can run on flex fuel.

MPG. Due to ethanol's lower energy content, FFVs operating on E85 get roughly 15% to 27% fewer miles per gallon than when operating on regular gasoline, depending on the ethanol content. Regular gasoline typically contains about 10% ethanol. ⁵

Cost. The cost of E85 relative to gasoline or E10 can vary due to location and fluctuations in energy markets. E85 is typically cheaper per gallon than gasoline but slightly more expensive per mile.

Performance. Drivers should notice no performance loss when using E85. In fact, some FFVs perform better-have more torque and horsepower-running on E85 than on regular gasoline. 6,7,8

Availability. More than 3,900 filling stations in the U.S. sell E85. Visit the Alternative Fueling Station Locator for service station locations.

Domestically produced (reduces oil dependence)

Lower emissions of some air pollutants

More resistant to engine knock

Added vehicle cost is negligible

Can only be used in flex-fuel vehicles

Lower energy content (lower gas mileage)

Limited availability

MotorWeek Videos

MotorWeek segments provided by Maryland Public Television

More Information

Fuel Economy Information for Ethanol Flexible Fuel Vehicles - Find a Car

Alternative Fuels Data Center

Environmental Protection Agency. E15: Frequently Asked Questions.

1. EIA. 2021. Monthly Energy Review, July 2021. p. 181.

2. EPA, Notice Of Decision Granting A Partial Waiver. "Partial Grant of Clean Air Act Waiver Application Submitted by Growth Energy To Increase the Allowable Ethanol Content of Gasoline to 15 Percent; Decision of the Administrator," Federal Register 76, no. 17 (January 26, 2011):4662.

3. Knoll, K., B. West, W. Clark, R. Graves, J. Orban, S. Przesmitzki, and T. Theiss. 2009. Effects of Intermediate Ethanol Blends on Legacy Vehicles and Small Non-Road Engines, Report 1 - Updated . NREL/TP-540-43543. National Renewable Energy Laboratory, Golden, Colorado, p. 3-3.

4. ASTM Standard D5798-11, "Standard Specification for Ethanol Fuel Blends for Flexible-Fuel Automotive Spark-Ignition Engines," ASTM International, West Conshohocken, PA, 2003, DOI: 10.1520/D5798-11, www.astm.org.

5. The fuel economy difference between using E85 and gasoline is given as a range since E85 includes blends containing 51% to 83% ethanol:

The lower bound (15% mpg decrease) is based on the difference in the energy content of a 51% ethanol blend and that of gasoline, which is typically 10% ethanol.

The upper bound (27% mpg decrease) is based on the difference in official EPA fuel economy tests of recent-model FFVs operating on ethanol-free gasoline and operating on E85.

6. General Motors. 2014 Chevrolet Silverado Specifications.

7. Thomas, J. F., S. P. Huff, and B. H. West. 2012. Fuel Economy and Emissions of a Vehicle Equipped with an Aftermarket Flexible-Fuel Conversion Kit . ORNL/TM-2011/483. Oak Ridge National Laboratory, Oak Ridge, Tennessee.

8. Thomas, J., B. West, and S. Huff. 2015. Effects of High-Octane Ethanol Blends on Four Legacy Flex-Fuel Vehicles, and a Turbocharged GDI Vehicle. ORNL/TM-2015/116. Oak Ridge National Laboratory, Oak Ridge, Tennessee.

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Ethanol is a renewable, domestically produced alcohol fuel made from plant material, such as corn, sugar cane, or grasses. Using ethanol can reduce oil dependence and greenhouse gas (GHG) emissions. Ethanol fuel use in the U.S. has increased dramatically from about 1.7 billion gallons in 2001 to about 12.6 billion in 2020.

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Electricity is an alternative fuel that can be used to power all-electric and plug-in hybrid cars. Powering vehicles with electricity can be cost-effective and can have significant energy security and emissions benefits.

Costs

It's typically cheaper to fuel a vehicle with electricity than gasoline or diesel. However, the vehicles are typically more expensive than their gasoline counterparts.

Federal tax credits of up to $7,500 are available for new plug-in vehicles to help offset these costs. State and local incentives are also available.

Annual fuel cost information on our site can help you determine whether a plug-in vehicle can save you money.

Availability (Charging)

The U.S. has an extensive electrical grid, and plug-in vehicles owners can re-charge their vehicles at home, work, or any of over 43,000 public charging stations across the country. The Department of Transportation is also establishing alternative fuel corridors along stretches of the U.S. highway system.

Visit Charging Your Plug-in Electric Car for more information about charging options.

Production

In the U.S., electricity is produced almost entirely from domestic resources. About two thirds is generated from fossil fuels, such as coal, natural gas, and petroleum. The rest is generated by nuclear power and renewables such as hydropower, solar, and wind.

Emissions

Powering a vehicle with electricity causes no tailpipe emissions, but pollutants and greenhouse gases (GHGs) may be emitted by the power plants that produce the electricity.

Generating electricity from fossil fuels produces more air pollutants and GHGs than generating it from nuclear, hydro-electric, wind, or solar power.

Our Beyond Tailpipe Emissions calculator can help you determine how much pollution and GHGs an electric-powered vehicle would emit in your area.

Many consumers that live in areas where the electricity is produced primarily from fossil fuels can still purchase Green Power to decrease their vehicle's impact on the environment.

Produced almost entirely from domestic resources

Typically more cost-efficient and prices more stable than gasoline

Vehicles can be charged at home

Availability of public charging stations growing rapidly

Electric motors are more efficient than internal combustion engines

Federal tax incentives available for plug-in vehicles; state and local incentives available in some areas

Consumers can purchase Green Power in many parts of U.S.

Less environmental advantages in areas where electricity is produced from fossil fuels

Vehicles are typically more expensive

Vehicle range is typically shorter than for gasoline and diesel vehicles

Re-charging takes significantly longer than re-fueling with other fuels

More Information
Electricity Electricity Explained: Electricity in the United States (EIA) Electric Vehicle Charging Station Locations Department of Transportation Alternative Fuel Corridors

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Electricity is an alternative fuel that can be used to power all-electric and plug-in hybrid cars. Powering vehicles with electricity can be cost-effective and can have significant energy security and emissions benefits. It's typically cheaper to fuel a vehicle with electricity than gasoline or diesel.

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Biodiesel is diesel fuel made from vegetable oils, animal fats, or recycled restaurant greases. It's safe, biodegradable, and produces less air pollutants than petroleum-based diesel.

Biodiesel can be used in its pure form (B100) or blended with petroleum diesel. Common blends include B2 (2% biodiesel), B5, and B20.

Most automakers approve blends up to B5. Some approve blends up to B20. Check with your owner's manual or automaker to determine the right blend for your vehicle. Using the wrong blend could damage your engine and/or void the manufacturer's warranty.

Note: Never fuel your car with grease or vegetable oil that has not been converted to biodiesel. It will damage your engine.

Domestically produced from renewable resources

Can be used in most diesel engines, especially newer ones

Less air pollutants (other than nitrogen oxides)

Less greenhouse gas emissions (e.g., B20 reduces CO₂ by 15%)

Biodegradable

Non-toxic

Safer to handle

Use of blends above B5 not yet approved by many automakers

Lower fuel economy and power (10% lower for B100, 2% for B20)

Currently more expensive

B100 generally not suitable for use in low temperatures

Concerns about B100's impact on engine durability

Slight increase in nitrogen oxide emissions in some circumstances

Biodiesel tends to cost more than petroleum diesel, and prices vary across the country. Visit DOE's Alternative Fuel Station Locator to find service stations selling biodiesel near you.

More Information

More on biodisel from DOE's Alternative Fuels Data Center (AFDC)
Biodiesel Basics Low-level Biodiesel Blends Just the Basics: Biodiesel Hydrogenation-Derived Renewable Diesel Alternative Fuel Price Report

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Biodiesel is diesel fuel made from vegetable oils, animal fats, or recycled restaurant greases. It's safe, biodegradable, and produces less air pollutants than petroleum-based diesel. Biodiesel can be used in its pure form (B100) or blended with petroleum diesel. Common blends include B2 (2% biodiesel), B5, and B20.

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Natural gas, a fossil fuel composed of mostly methane, is one of the cleanest burning alternative fuels. It can be used in the form of compressed natural gas (CNG) or liquefied natural gas (LNG) to fuel cars and trucks.

Dedicated natural gas vehicles are designed to run on natural gas only, while bi-fuel vehicles can also run on gasoline or diesel. Bi-fuel vehicles allow users to take advantage of the wide-spread availability of gasoline or diesel but use a cleaner, more economical alternative when natural gas is available. Since natural gas is stored in high-pressure fuel tanks, bi-fuel vehicles require two separate fueling systems, which take up passenger/cargo space.

Natural gas vehicles are not available on a large scale in the U.S.-only a few models are currently offered for sale. However, conventional gasoline and diesel vehicles can be retrofitted for CNG.

All natural gas used in the U.S. is domestically produced¹

Up to 10% less greenhouse gas emissions²

Roughly half as much particulate emissions that can cause harmful health effects²

Less expensive than gasoline

Limited vehicle availability

Less readily available than gasoline and diesel

Fewer miles on a tank of fuel

Additional Information

Fuel Economy Information for Bi-fuel and Natural Gas (CNG) Vehicles - Find a Car

Alternative Fuels and Advanced Vehicles Data Center

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Natural gas, a fossil fuel composed of mostly methane, is one of the cleanest burning alternative fuels. It can be used in the form of compressed natural gas (CNG) or liquefied natural gas (LNG) to fuel cars and trucks. Dedicated natural gas vehicles are designed to run on natural gas only, while bi-fuel vehicles can also run on gasoline or diesel.

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Natural gas, a fossil fuel composed of mostly methane, is one of the cleanest burning alternative fuels. It can be used in the form of compressed natural gas (CNG) or liquefied natural gas (LNG) to fuel cars and trucks.

Dedicated natural gas vehicles are designed to run on natural gas only, while bi-fuel vehicles can also run on gasoline or diesel. Bi-fuel vehicles allow users to take advantage of the wide-spread availability of gasoline or diesel but use a cleaner, more economical alternative when natural gas is available. Since natural gas is stored in high-pressure fuel tanks, bi-fuel vehicles require two separate fueling systems, which take up passenger/cargo space.

Natural gas vehicles are not available on a large scale in the U.S.-only a few models are currently offered for sale. However, conventional gasoline and diesel vehicles can be retrofitted for CNG.

All natural gas used in the U.S. is domestically produced¹

Up to 10% less greenhouse gas emissions²

Roughly half as much particulate emissions that can cause harmful health effects²

Less expensive than gasoline

Limited vehicle availability

Less readily available than gasoline and diesel

Fewer miles on a tank of fuel

Additional Information

Fuel Economy Information for Bi-fuel and Natural Gas (CNG) Vehicles - Find a Car

Alternative Fuels and Advanced Vehicles Data Center

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Natural gas, a fossil fuel composed of mostly methane, is one of the cleanest burning alternative fuels. It can be used in the form of compressed natural gas (CNG) or liquefied natural gas (LNG) to fuel cars and trucks. Dedicated natural gas vehicles are designed to run on natural gas only, while bi-fuel vehicles can also run on gasoline or diesel.

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Hydrogen can power passenger vehicles. It can be used in fuel cells to power electric motors or burned in internal combustion engines (ICEs).

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Propane, or liquefied petroleum gas (LPG), is a clean-burning fossil fuel that can be used in internal combustion engines.

Most of the propane used in the U.S. is produced domestically. It is usually cheaper than gasoline and does not degrade performance. LPG-fueled vehicles can also emit lower amounts of some air pollutants and greenhouse gases, depending on vehicle type, calibration, and drive cycle.

The drawbacks to LPG are the limited number of fueling stations and vehicles. Over 900 public fueling stations sell LPG. A few light-duty vehicles-mostly larger trucks and vans-can be ordered from a dealer with a prep-ready engine package and converted to use propane. Consumers can also convert in-use conventional vehicles for LPG use. Some LPG vehicles run on propane only. Others can switch between propane and a conventional fuel such as gasoline.

Propane is stored as a liquid in pressurized fuel tanks rated to 300 psi. So, LPG conversions consist of installing a separate fuel system (if the vehicle will use both conventional fuel and LPG) or a replacement fuel system (LPG-only operation).

Converting a vehicle to use LPG can cost $6,000 to $12,000. However, this cost may be recovered in lower fuel and maintenance costs.

86% of propane used in the U.S. comes from domestic sources¹

Cheaper than gasoline

Lower vehicle maintenance costs

Potentially lower toxic, carbon dioxide (CO₂), carbon monoxide (CO), and non-methane hydrocarbon (NMHC) emissions

Limited vehicle availability

Limited number of fueling stations

Fewer miles on a tank of fuel

Converting a vehicle to use LPG is expensive

Additional Information
Fuel Economy Information for Alternative Fuel Vehicles
Alternative Fuels Data Center (U.S. Department of Energy)

Energy Information Administration (U.S. Department of Energy)

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Propane, or liquefied petroleum gas (LPG), is a clean-burning fossil fuel that can be used in internal combustion engines. Most of the propane used in the U.S. is produced domestically. It is usually cheaper than gasoline and does not degrade performance.

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Fuel cells produce electricity from a number of domestic fuels, including hydrogen and renewables, and can provide power for virtually any application -- from cars and buses to commercial buildings. The Fuel Cell Technologies Office (FCTO) focuses on applied research, development, and innovation to advance hydrogen and fuel cells for transportation and diverse applications enabling energy security, resiliency, and a strong domestic economy in emerging technologies.

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Fuel cells produce electricity from a number of domestic fuels, including hydrogen and renewables, and can provide power for virtually any application -- from cars and buses to commercial buildings. The Fuel Cell Technologies Office (FCTO) focuses on applied research, development, and innovation to advance hydrogen and fuel cells for transportation and diverse applications enabling energy security, resiliency, and a strong domestic economy in emerging technologies.

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It happens every summer, and no one likes it. No, we're not talking about farmer's tans or your neighbor deciding that 6 a.m. is an appropriate time to mow the lawn. We're talking about the summer spike in gas prices. The summer of 2008 was one of the worst, with the average nationwide gas price peaking at over $4 per gallon -- making topping off the tank something you could do only after checking your bank account balance first.

With memories of that summer still fresh in our minds and new gas price hikes looming, it's natural to wonder what alternatives there may be to gasoline-powered vehicles. Well, as it turns out, there are lots of alternatives. And many of them are on the road or in dealerships right now. While some alternatives will take some time to make it into wide usage, check out this list of the top 10 alternative fuels on the road now.

Using hydrogen to fuel your car may conjure up "Oh the humanity!" images of the Hindenburg, but it's actually quite safe. Hydrogen can actually fuel two different types of cars: fuel cell vehicles and vehicles that have an internal combustion engine that's been engineered to use hydrogen instead of gasoline.

In a fuel-cell vehicle, the hydrogen is used to generate electricity that's then used to power electric motors. So, rather than running strictly off of battery power alone, a hydrogen-powered car uses a fuel cell to generate its own electricity. In a chemical process within the fuel cell, hydrogen and oxygen are combined to create electricity, and the only byproduct of this process is water vapor. The Honda FCX Clarity uses this technology and is currently being leased to drivers in southern California.

In a hydrogen combustion engine, the car uses an internal combustion engine just like a gasoline-powered car, but instead of gasoline, hydrogen is the fuel source. Instead of harmful CO2 emissions, like gasoline cars produce, again, hydrogen cars produce only water vapor. Lots of automakers are currently testing hydrogen vehicles. Currently, the BMW Hydrogen 7 is perhaps the most famous; the company has leased several to high-profile individuals in Germany and the United States, and some tests have even shown that the car actually cleans the air around it [source: U.S. News Rankings and Reviews].

Hydrogen cars aren't widespread largely because there isn't the necessary infrastructure of hydrogen fueling stations. But our next alternative fuel is somewhat easier to find -- in fact, you're using some right now.

It may seem like electric cars have been a long time coming, but the fact is, some of the earliest automobiles used electric motors. However, it's only due to recent developments that electric cars have become a more viable method for everyday travel.

So, what's been the hold up? Battery technology. Moving a car takes a lot of power, and having to do it at high speeds and over long distances can significantly drain an electric car's batteries. In the past, electric cars couldn't go very far, and once their batteries were dead, they could take hours and hours to recharge.

However, with new battery technology, some automakers are overcoming these limitations. The new batteries ( lithium-ion batteries, to be exact) are the same kind that power your cell phone or laptop. They charge quickly and the charges last longer, too. Cars like the Tesla Roadster use them to get supercar performance from their electric motors. Other cars that are soon to be on the market, like the Chevy Volt, for example, use these types of batteries in combination with an internal combustion engine to create a new class of automobile called an extended-range electric vehicle. The batteries can be charged by plugging the car into a regular wall outlet; however, when the battery power begins to fade, an onboard gasoline generator switches on to recharge the batteries and keep the car going.

We hope you've gotten the message that a low-fat diet with limited quantities of fried foods is good for your health. However, the same doesn't necessarily hold true for your car.

Biodiesel is a type of fuel made from cooking oil and grease. Any car with a diesel engine can run on it -- but don't start wringing the napkins from your last McDonald's run into your fuel tank. In order to power the car, the oil and grease need to be converted into biodiesel through a chemical process.

The process itself can actually be done at home. In fact, a lot of biodiesel enthusiasts make their own fuel using cooking oil from local restaurants. However, there is a little risk involved with the process. If you get it wrong, you could do a lot of damage to your vehicle (not to mention your house and yourself). Before trying to make biodiesel on your own, it's a good idea to train for a while with someone who's successfully done it before.

Biodiesel enthusiasts swear by the stuff. Not only is it much cheaper and cleaner than fossil diesel, but it'll make your car smell like french fries, too. No kidding! Just make sure you and your car can handle it before you brew up a batch.

So now you know that you can run a car on fry grease, but what if you're a little more heath conscious and don't necessarily want to drive around town smelling of fries? What are your other options? Well, how about making sure your car gets its fresh vegetables, too?

Ethanol is an increasingly common alternative fuel. In fact, it's often added to gasoline in the summertime to help cut emissions. Ethanol is a type of alcohol (but don't even think about drinking it) that's made from plant matter. In the United States it's commonly made from corn, while in other countries, like Brazil, it's made from sugar cane.

Lots of automakers offer their cars with flex-fuel engines. These engines can run on either standard gasoline from the pump or E85 ethanol, a fuel blend that's 15 percent gasoline and 85 percent ethanol. Ethanol has been widely hailed as a good way to end America's addition to foreign oil. After all, we can grow this fuel domestically, and it's not a finite resource like oil is. Still, it takes a lot of energy to create ethanol. Also, some people say that since farmers can make more money growing crops for ethanol, they'll stop growing crops for food, which could drive food prices up.

Despite these concerns, ethanol offers a lot of benefits as an alternative fuel, and the network of ethanol fueling stations continues to increase.

Not to push the cooking theme too hard, but the next alternative fuel that's already on the road is similar to stuff you may have in your kitchen as well. Unlike ethanol or biodiesel, it's not created using something you could eat or drink, but it is something that top chefs insist on cooking with: natural gas.

Natural gas is a fossil fuel that's found between layers of underground rock. It's drilled for, like oil, but there's a lot more of it available here in the United States and it burns cleaner than oil or gasoline. The natural gas that you may use to cook your food and heat your bathwater is natural gas in a very low-pressure form. That keeps this particular fuel in a gaseous state and means that it releases a relatively small amount of energy when it's burned.

However, if you cool natural gas, it becomes liquefied. And when it's liquefied, it becomes much more energy dense. When liquefied natural gas (LNG) is burned, it releases much more energy. So, for example, instead of simply heating up some soup, like low-pressure natural gas is capable of doing quite well, liquefied natural gas can power large equipment, like a truck. And that's just what it's used for -- powering heavy-duty trucks over long distances.

If you've been to a cookout recently, you're probably familiar with our next alternative fuel: liquefied petroleum gas, or LP gas. Still not sure if you've seen it? Well, do you ever grill with propane?

Propane is the common name for liquefied petroleum gas, although that's not exactly right. LP gas is a hydrocarbon gas under low pressure. It's made up mainly of propane, but it also includes other hydrocarbon gases. LP gas is kept pressurized in order to keep it in liquid form. Similar to liquefied natural gas, keeping LP gas liquefied makes it more energy dense, and thus more useful for powering cars and trucks.

LP gas powers a car through an internal combustion engine that's been engineered for that type of fuel. While this type of fuel isn't widely used for cars in the United States, LP gas accounts for 10 percent of automotive fuel in the Netherlands, and lots of other counties have experimented with it, too [source: California Energy Commission].

What if, instead of heading to the gas station when you needed to fuel up your car, you had a fuel line running to your house, ready whenever you needed it?

With a compressed natural gas (CNG) car, you already do (well, probably). Compressed natural gas is the same fuel you might use in your home for cooking and heating, and it runs to your home in a line supplied by the gas company. For a CNG vehicle, the gas is stored in high-pressure cylinders. When you have a compressed natural gas vehicle, there's actually a little more to the process than just hooking up to the nearest stove fitting. You'll also need a fueling station in your house that's capable of compressing the gas. The compressed gas is then stored in the car's fuel tank (or tanks), as CNG takes up a greater amount of space than gasoline does.

Honda introduced the Honda Civic GX in 1998. The Civic GX is a regular Honda Civic that runs on compressed natural gas. As CNG is cheaper and burns cleaner than gasoline, these types of cars may gain popularity -- especially if the initial expense of installing a fuel station in a home is offset by savings on fuel. One downside, however, is that there isn't yet a nationwide network of fuel stations offering compressed natural gas -- which means that if you run out of fuel when you're far from home, you're simply out of luck.

Air is everywhere, so why not use it to fuel cars? Well, compressed air cars can do just that.

In this type of vehicle, air is compressed in high-pressure tubes. While a typical engine uses air mixed with gasoline (or diesel fuel) which is then ignited with a spark (or high-pressure) to generate power, a compressed-air vehicle's engine makes use of the expansion of the compressed air as it's released from the high-pressure tubes to drive the engine's pistons.

But compressed-air cars don't run entirely on air. Electric motors are also on-board to compress the air into the car's high-pressure tubes. However, these cars can't be considered fully electric cars either, mainly because the motors don't directly power the wheels. The electric motors are much smaller than the electric motors used in other electric cars where the primary function of the motor is to power the wheels. Compressed-air cars do have to be charged, similar to an electric car, but because the motors use much less energy, the charge time tends to be much less, too.

Liquid nitrogen is another alternative fuel. Like hydrogen, nitrogen is abundant in our atmosphere. Also like hydrogen, nitrogen-powered cars make fewer harmful emissions than gasoline or diesel. But while hydrogen is used in fuel cell cars as well as hydrogen-combustion engines, liquid nitrogen cars use a different type of engine altogether.

In fact, a liquid nitrogen car uses an engine similar to the engine used in a compressed-air car. In a liquid nitrogen car, the nitrogen is kept cold, keeping it in a liquid form. To power the car, the nitrogen is released into the engine where it is heated and it expands to create energy. While a typical gasoline- or diesel-powered engine uses combustion to move pistons, a liquid nitrogen engine uses the expanding nitrogen to power turbines.

While it's a clean an efficient way to power a vehicle, liquid nitrogen faces the same hurdles as many other alternative fuels: At this time, there's no nationwide network of fueling stations to deliver it to consumers.

The final alternative fuel on our list is probably a surprise. So, how can coal fuel cars?

Technically, coal is a relatively new alternative fuel for cars -- indirectly, anyway. As electric cars, plug-in hybrids and extended-range electric vehicles become more common, coal will be fueling more and more cars. How exactly? Well, owners aren't going to have to shovel buckets of the stuff into incinerators, if that's what you're wondering.

Electric vehicles (for the most part), don't make their own electricity. They carry the energy in their charged batteries. And the batteries get their charge from a standard wall outlet, which gets its power from an electricity plant, which, in turn, gets its power from burning coal. In fact, 50 percent of all of the electricity in the United States comes from coal-fired plants [source: PBS.org]. That means that, when you go all the way down the energy chain, a lot of electric cars are actually coal-powered cars.

While coal has similar drawbacks to gasoline, it also has some benefits. On a per-mile basis, electricity from coal is a cheaper way to power a car than gasoline. Also, there's plenty of coal in the United States, so international relations shouldn't disrupt the supply too much. Also, people who get their electricity from other sources, such as hydro-electric power plants or nuclear power plants, can charge their electric cars without creating more coal emissions.

Still, the fact that some of the most anticipated clean cars heading to your local dealership will likely get their energy from a less-than-clean source just goes to show you that in the world of energy, there's no such thing as a free lunch.

For more information about alternative fuels, hybrid cars and other related topics, follow the links on the next page.

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Top 10 Alternative Fuels on the Road Right Now

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It happens every summer, and no one likes it. No, we're not talking about farmer's tans or your neighbor deciding that 6 a.m. is an appropriate time to mow the lawn. We're talking about the summer spike in gas prices.

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It happens every summer, and no one likes it. No, we're not talking about farmer's tans or your neighbor deciding that 6 a.m. is an appropriate time to mow the lawn. We're talking about the summer spike in gas prices. The summer of 2008 was one of the worst, with the average nationwide gas price peaking at over $4 per gallon -- making topping off the tank something you could do only after checking your bank account balance first.

With memories of that summer still fresh in our minds and new gas price hikes looming, it's natural to wonder what alternatives there may be to gasoline-powered vehicles. Well, as it turns out, there are lots of alternatives. And many of them are on the road or in dealerships right now. While some alternatives will take some time to make it into wide usage, check out this list of the top 10 alternative fuels on the road now.

Using hydrogen to fuel your car may conjure up "Oh the humanity!" images of the Hindenburg, but it's actually quite safe. Hydrogen can actually fuel two different types of cars: fuel cell vehicles and vehicles that have an internal combustion engine that's been engineered to use hydrogen instead of gasoline.

In a fuel-cell vehicle, the hydrogen is used to generate electricity that's then used to power electric motors. So, rather than running strictly off of battery power alone, a hydrogen-powered car uses a fuel cell to generate its own electricity. In a chemical process within the fuel cell, hydrogen and oxygen are combined to create electricity, and the only byproduct of this process is water vapor. The Honda FCX Clarity uses this technology and is currently being leased to drivers in southern California.

In a hydrogen combustion engine, the car uses an internal combustion engine just like a gasoline-powered car, but instead of gasoline, hydrogen is the fuel source. Instead of harmful CO2 emissions, like gasoline cars produce, again, hydrogen cars produce only water vapor. Lots of automakers are currently testing hydrogen vehicles. Currently, the BMW Hydrogen 7 is perhaps the most famous; the company has leased several to high-profile individuals in Germany and the United States, and some tests have even shown that the car actually cleans the air around it [source: U.S. News Rankings and Reviews].

Hydrogen cars aren't widespread largely because there isn't the necessary infrastructure of hydrogen fueling stations. But our next alternative fuel is somewhat easier to find -- in fact, you're using some right now.

It may seem like electric cars have been a long time coming, but the fact is, some of the earliest automobiles used electric motors. However, it's only due to recent developments that electric cars have become a more viable method for everyday travel.

So, what's been the hold up? Battery technology. Moving a car takes a lot of power, and having to do it at high speeds and over long distances can significantly drain an electric car's batteries. In the past, electric cars couldn't go very far, and once their batteries were dead, they could take hours and hours to recharge.

However, with new battery technology, some automakers are overcoming these limitations. The new batteries ( lithium-ion batteries, to be exact) are the same kind that power your cell phone or laptop. They charge quickly and the charges last longer, too. Cars like the Tesla Roadster use them to get supercar performance from their electric motors. Other cars that are soon to be on the market, like the Chevy Volt, for example, use these types of batteries in combination with an internal combustion engine to create a new class of automobile called an extended-range electric vehicle. The batteries can be charged by plugging the car into a regular wall outlet; however, when the battery power begins to fade, an onboard gasoline generator switches on to recharge the batteries and keep the car going.

We hope you've gotten the message that a low-fat diet with limited quantities of fried foods is good for your health. However, the same doesn't necessarily hold true for your car.

Biodiesel is a type of fuel made from cooking oil and grease. Any car with a diesel engine can run on it -- but don't start wringing the napkins from your last McDonald's run into your fuel tank. In order to power the car, the oil and grease need to be converted into biodiesel through a chemical process.

The process itself can actually be done at home. In fact, a lot of biodiesel enthusiasts make their own fuel using cooking oil from local restaurants. However, there is a little risk involved with the process. If you get it wrong, you could do a lot of damage to your vehicle (not to mention your house and yourself). Before trying to make biodiesel on your own, it's a good idea to train for a while with someone who's successfully done it before.

Biodiesel enthusiasts swear by the stuff. Not only is it much cheaper and cleaner than fossil diesel, but it'll make your car smell like french fries, too. No kidding! Just make sure you and your car can handle it before you brew up a batch.

So now you know that you can run a car on fry grease, but what if you're a little more heath conscious and don't necessarily want to drive around town smelling of fries? What are your other options? Well, how about making sure your car gets its fresh vegetables, too?

Ethanol is an increasingly common alternative fuel. In fact, it's often added to gasoline in the summertime to help cut emissions. Ethanol is a type of alcohol (but don't even think about drinking it) that's made from plant matter. In the United States it's commonly made from corn, while in other countries, like Brazil, it's made from sugar cane.

Lots of automakers offer their cars with flex-fuel engines. These engines can run on either standard gasoline from the pump or E85 ethanol, a fuel blend that's 15 percent gasoline and 85 percent ethanol. Ethanol has been widely hailed as a good way to end America's addition to foreign oil. After all, we can grow this fuel domestically, and it's not a finite resource like oil is. Still, it takes a lot of energy to create ethanol. Also, some people say that since farmers can make more money growing crops for ethanol, they'll stop growing crops for food, which could drive food prices up.

Despite these concerns, ethanol offers a lot of benefits as an alternative fuel, and the network of ethanol fueling stations continues to increase.

Not to push the cooking theme too hard, but the next alternative fuel that's already on the road is similar to stuff you may have in your kitchen as well. Unlike ethanol or biodiesel, it's not created using something you could eat or drink, but it is something that top chefs insist on cooking with: natural gas.

Natural gas is a fossil fuel that's found between layers of underground rock. It's drilled for, like oil, but there's a lot more of it available here in the United States and it burns cleaner than oil or gasoline. The natural gas that you may use to cook your food and heat your bathwater is natural gas in a very low-pressure form. That keeps this particular fuel in a gaseous state and means that it releases a relatively small amount of energy when it's burned.

However, if you cool natural gas, it becomes liquefied. And when it's liquefied, it becomes much more energy dense. When liquefied natural gas (LNG) is burned, it releases much more energy. So, for example, instead of simply heating up some soup, like low-pressure natural gas is capable of doing quite well, liquefied natural gas can power large equipment, like a truck. And that's just what it's used for -- powering heavy-duty trucks over long distances.

If you've been to a cookout recently, you're probably familiar with our next alternative fuel: liquefied petroleum gas, or LP gas. Still not sure if you've seen it? Well, do you ever grill with propane?

Propane is the common name for liquefied petroleum gas, although that's not exactly right. LP gas is a hydrocarbon gas under low pressure. It's made up mainly of propane, but it also includes other hydrocarbon gases. LP gas is kept pressurized in order to keep it in liquid form. Similar to liquefied natural gas, keeping LP gas liquefied makes it more energy dense, and thus more useful for powering cars and trucks.

LP gas powers a car through an internal combustion engine that's been engineered for that type of fuel. While this type of fuel isn't widely used for cars in the United States, LP gas accounts for 10 percent of automotive fuel in the Netherlands, and lots of other counties have experimented with it, too [source: California Energy Commission].

What if, instead of heading to the gas station when you needed to fuel up your car, you had a fuel line running to your house, ready whenever you needed it?

With a compressed natural gas (CNG) car, you already do (well, probably). Compressed natural gas is the same fuel you might use in your home for cooking and heating, and it runs to your home in a line supplied by the gas company. For a CNG vehicle, the gas is stored in high-pressure cylinders. When you have a compressed natural gas vehicle, there's actually a little more to the process than just hooking up to the nearest stove fitting. You'll also need a fueling station in your house that's capable of compressing the gas. The compressed gas is then stored in the car's fuel tank (or tanks), as CNG takes up a greater amount of space than gasoline does.

Honda introduced the Honda Civic GX in 1998. The Civic GX is a regular Honda Civic that runs on compressed natural gas. As CNG is cheaper and burns cleaner than gasoline, these types of cars may gain popularity -- especially if the initial expense of installing a fuel station in a home is offset by savings on fuel. One downside, however, is that there isn't yet a nationwide network of fuel stations offering compressed natural gas -- which means that if you run out of fuel when you're far from home, you're simply out of luck.

Air is everywhere, so why not use it to fuel cars? Well, compressed air cars can do just that.

In this type of vehicle, air is compressed in high-pressure tubes. While a typical engine uses air mixed with gasoline (or diesel fuel) which is then ignited with a spark (or high-pressure) to generate power, a compressed-air vehicle's engine makes use of the expansion of the compressed air as it's released from the high-pressure tubes to drive the engine's pistons.

But compressed-air cars don't run entirely on air. Electric motors are also on-board to compress the air into the car's high-pressure tubes. However, these cars can't be considered fully electric cars either, mainly because the motors don't directly power the wheels. The electric motors are much smaller than the electric motors used in other electric cars where the primary function of the motor is to power the wheels. Compressed-air cars do have to be charged, similar to an electric car, but because the motors use much less energy, the charge time tends to be much less, too.

Liquid nitrogen is another alternative fuel. Like hydrogen, nitrogen is abundant in our atmosphere. Also like hydrogen, nitrogen-powered cars make fewer harmful emissions than gasoline or diesel. But while hydrogen is used in fuel cell cars as well as hydrogen-combustion engines, liquid nitrogen cars use a different type of engine altogether.

In fact, a liquid nitrogen car uses an engine similar to the engine used in a compressed-air car. In a liquid nitrogen car, the nitrogen is kept cold, keeping it in a liquid form. To power the car, the nitrogen is released into the engine where it is heated and it expands to create energy. While a typical gasoline- or diesel-powered engine uses combustion to move pistons, a liquid nitrogen engine uses the expanding nitrogen to power turbines.

While it's a clean an efficient way to power a vehicle, liquid nitrogen faces the same hurdles as many other alternative fuels: At this time, there's no nationwide network of fueling stations to deliver it to consumers.

The final alternative fuel on our list is probably a surprise. So, how can coal fuel cars?

Technically, coal is a relatively new alternative fuel for cars -- indirectly, anyway. As electric cars, plug-in hybrids and extended-range electric vehicles become more common, coal will be fueling more and more cars. How exactly? Well, owners aren't going to have to shovel buckets of the stuff into incinerators, if that's what you're wondering.

Electric vehicles (for the most part), don't make their own electricity. They carry the energy in their charged batteries. And the batteries get their charge from a standard wall outlet, which gets its power from an electricity plant, which, in turn, gets its power from burning coal. In fact, 50 percent of all of the electricity in the United States comes from coal-fired plants [source: PBS.org]. That means that, when you go all the way down the energy chain, a lot of electric cars are actually coal-powered cars.

While coal has similar drawbacks to gasoline, it also has some benefits. On a per-mile basis, electricity from coal is a cheaper way to power a car than gasoline. Also, there's plenty of coal in the United States, so international relations shouldn't disrupt the supply too much. Also, people who get their electricity from other sources, such as hydro-electric power plants or nuclear power plants, can charge their electric cars without creating more coal emissions.

Still, the fact that some of the most anticipated clean cars heading to your local dealership will likely get their energy from a less-than-clean source just goes to show you that in the world of energy, there's no such thing as a free lunch.

For more information about alternative fuels, hybrid cars and other related topics, follow the links on the next page.

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Top 10 Alternative Fuels on the Road Right Now

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It happens every summer, and no one likes it. No, we're not talking about farmer's tans or your neighbor deciding that 6 a.m. is an appropriate time to mow the lawn. We're talking about the summer spike in gas prices.

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It happens every summer, and no one likes it. No, we're not talking about farmer's tans or your neighbor deciding that 6 a.m. is an appropriate time to mow the lawn. We're talking about the summer spike in gas prices. The summer of 2008 was one of the worst, with the average nationwide gas price peaking at over $4 per gallon -- making topping off the tank something you could do only after checking your bank account balance first.

With memories of that summer still fresh in our minds and new gas price hikes looming, it's natural to wonder what alternatives there may be to gasoline-powered vehicles. Well, as it turns out, there are lots of alternatives. And many of them are on the road or in dealerships right now. While some alternatives will take some time to make it into wide usage, check out this list of the top 10 alternative fuels on the road now.

Using hydrogen to fuel your car may conjure up "Oh the humanity!" images of the Hindenburg, but it's actually quite safe. Hydrogen can actually fuel two different types of cars: fuel cell vehicles and vehicles that have an internal combustion engine that's been engineered to use hydrogen instead of gasoline.

In a fuel-cell vehicle, the hydrogen is used to generate electricity that's then used to power electric motors. So, rather than running strictly off of battery power alone, a hydrogen-powered car uses a fuel cell to generate its own electricity. In a chemical process within the fuel cell, hydrogen and oxygen are combined to create electricity, and the only byproduct of this process is water vapor. The Honda FCX Clarity uses this technology and is currently being leased to drivers in southern California.

In a hydrogen combustion engine, the car uses an internal combustion engine just like a gasoline-powered car, but instead of gasoline, hydrogen is the fuel source. Instead of harmful CO2 emissions, like gasoline cars produce, again, hydrogen cars produce only water vapor. Lots of automakers are currently testing hydrogen vehicles. Currently, the BMW Hydrogen 7 is perhaps the most famous; the company has leased several to high-profile individuals in Germany and the United States, and some tests have even shown that the car actually cleans the air around it [source: U.S. News Rankings and Reviews].

Hydrogen cars aren't widespread largely because there isn't the necessary infrastructure of hydrogen fueling stations. But our next alternative fuel is somewhat easier to find -- in fact, you're using some right now.

It may seem like electric cars have been a long time coming, but the fact is, some of the earliest automobiles used electric motors. However, it's only due to recent developments that electric cars have become a more viable method for everyday travel.

So, what's been the hold up? Battery technology. Moving a car takes a lot of power, and having to do it at high speeds and over long distances can significantly drain an electric car's batteries. In the past, electric cars couldn't go very far, and once their batteries were dead, they could take hours and hours to recharge.

However, with new battery technology, some automakers are overcoming these limitations. The new batteries ( lithium-ion batteries, to be exact) are the same kind that power your cell phone or laptop. They charge quickly and the charges last longer, too. Cars like the Tesla Roadster use them to get supercar performance from their electric motors. Other cars that are soon to be on the market, like the Chevy Volt, for example, use these types of batteries in combination with an internal combustion engine to create a new class of automobile called an extended-range electric vehicle. The batteries can be charged by plugging the car into a regular wall outlet; however, when the battery power begins to fade, an onboard gasoline generator switches on to recharge the batteries and keep the car going.

We hope you've gotten the message that a low-fat diet with limited quantities of fried foods is good for your health. However, the same doesn't necessarily hold true for your car.

Biodiesel is a type of fuel made from cooking oil and grease. Any car with a diesel engine can run on it -- but don't start wringing the napkins from your last McDonald's run into your fuel tank. In order to power the car, the oil and grease need to be converted into biodiesel through a chemical process.

The process itself can actually be done at home. In fact, a lot of biodiesel enthusiasts make their own fuel using cooking oil from local restaurants. However, there is a little risk involved with the process. If you get it wrong, you could do a lot of damage to your vehicle (not to mention your house and yourself). Before trying to make biodiesel on your own, it's a good idea to train for a while with someone who's successfully done it before.

Biodiesel enthusiasts swear by the stuff. Not only is it much cheaper and cleaner than fossil diesel, but it'll make your car smell like french fries, too. No kidding! Just make sure you and your car can handle it before you brew up a batch.

So now you know that you can run a car on fry grease, but what if you're a little more heath conscious and don't necessarily want to drive around town smelling of fries? What are your other options? Well, how about making sure your car gets its fresh vegetables, too?

Ethanol is an increasingly common alternative fuel. In fact, it's often added to gasoline in the summertime to help cut emissions. Ethanol is a type of alcohol (but don't even think about drinking it) that's made from plant matter. In the United States it's commonly made from corn, while in other countries, like Brazil, it's made from sugar cane.

Lots of automakers offer their cars with flex-fuel engines. These engines can run on either standard gasoline from the pump or E85 ethanol, a fuel blend that's 15 percent gasoline and 85 percent ethanol. Ethanol has been widely hailed as a good way to end America's addition to foreign oil. After all, we can grow this fuel domestically, and it's not a finite resource like oil is. Still, it takes a lot of energy to create ethanol. Also, some people say that since farmers can make more money growing crops for ethanol, they'll stop growing crops for food, which could drive food prices up.

Despite these concerns, ethanol offers a lot of benefits as an alternative fuel, and the network of ethanol fueling stations continues to increase.

Not to push the cooking theme too hard, but the next alternative fuel that's already on the road is similar to stuff you may have in your kitchen as well. Unlike ethanol or biodiesel, it's not created using something you could eat or drink, but it is something that top chefs insist on cooking with: natural gas.

Natural gas is a fossil fuel that's found between layers of underground rock. It's drilled for, like oil, but there's a lot more of it available here in the United States and it burns cleaner than oil or gasoline. The natural gas that you may use to cook your food and heat your bathwater is natural gas in a very low-pressure form. That keeps this particular fuel in a gaseous state and means that it releases a relatively small amount of energy when it's burned.

However, if you cool natural gas, it becomes liquefied. And when it's liquefied, it becomes much more energy dense. When liquefied natural gas (LNG) is burned, it releases much more energy. So, for example, instead of simply heating up some soup, like low-pressure natural gas is capable of doing quite well, liquefied natural gas can power large equipment, like a truck. And that's just what it's used for -- powering heavy-duty trucks over long distances.

If you've been to a cookout recently, you're probably familiar with our next alternative fuel: liquefied petroleum gas, or LP gas. Still not sure if you've seen it? Well, do you ever grill with propane?

Propane is the common name for liquefied petroleum gas, although that's not exactly right. LP gas is a hydrocarbon gas under low pressure. It's made up mainly of propane, but it also includes other hydrocarbon gases. LP gas is kept pressurized in order to keep it in liquid form. Similar to liquefied natural gas, keeping LP gas liquefied makes it more energy dense, and thus more useful for powering cars and trucks.

LP gas powers a car through an internal combustion engine that's been engineered for that type of fuel. While this type of fuel isn't widely used for cars in the United States, LP gas accounts for 10 percent of automotive fuel in the Netherlands, and lots of other counties have experimented with it, too [source: California Energy Commission].

What if, instead of heading to the gas station when you needed to fuel up your car, you had a fuel line running to your house, ready whenever you needed it?

With a compressed natural gas (CNG) car, you already do (well, probably). Compressed natural gas is the same fuel you might use in your home for cooking and heating, and it runs to your home in a line supplied by the gas company. For a CNG vehicle, the gas is stored in high-pressure cylinders. When you have a compressed natural gas vehicle, there's actually a little more to the process than just hooking up to the nearest stove fitting. You'll also need a fueling station in your house that's capable of compressing the gas. The compressed gas is then stored in the car's fuel tank (or tanks), as CNG takes up a greater amount of space than gasoline does.

Honda introduced the Honda Civic GX in 1998. The Civic GX is a regular Honda Civic that runs on compressed natural gas. As CNG is cheaper and burns cleaner than gasoline, these types of cars may gain popularity -- especially if the initial expense of installing a fuel station in a home is offset by savings on fuel. One downside, however, is that there isn't yet a nationwide network of fuel stations offering compressed natural gas -- which means that if you run out of fuel when you're far from home, you're simply out of luck.

Air is everywhere, so why not use it to fuel cars? Well, compressed air cars can do just that.

In this type of vehicle, air is compressed in high-pressure tubes. While a typical engine uses air mixed with gasoline (or diesel fuel) which is then ignited with a spark (or high-pressure) to generate power, a compressed-air vehicle's engine makes use of the expansion of the compressed air as it's released from the high-pressure tubes to drive the engine's pistons.

But compressed-air cars don't run entirely on air. Electric motors are also on-board to compress the air into the car's high-pressure tubes. However, these cars can't be considered fully electric cars either, mainly because the motors don't directly power the wheels. The electric motors are much smaller than the electric motors used in other electric cars where the primary function of the motor is to power the wheels. Compressed-air cars do have to be charged, similar to an electric car, but because the motors use much less energy, the charge time tends to be much less, too.

Liquid nitrogen is another alternative fuel. Like hydrogen, nitrogen is abundant in our atmosphere. Also like hydrogen, nitrogen-powered cars make fewer harmful emissions than gasoline or diesel. But while hydrogen is used in fuel cell cars as well as hydrogen-combustion engines, liquid nitrogen cars use a different type of engine altogether.

In fact, a liquid nitrogen car uses an engine similar to the engine used in a compressed-air car. In a liquid nitrogen car, the nitrogen is kept cold, keeping it in a liquid form. To power the car, the nitrogen is released into the engine where it is heated and it expands to create energy. While a typical gasoline- or diesel-powered engine uses combustion to move pistons, a liquid nitrogen engine uses the expanding nitrogen to power turbines.

While it's a clean an efficient way to power a vehicle, liquid nitrogen faces the same hurdles as many other alternative fuels: At this time, there's no nationwide network of fueling stations to deliver it to consumers.

The final alternative fuel on our list is probably a surprise. So, how can coal fuel cars?

Technically, coal is a relatively new alternative fuel for cars -- indirectly, anyway. As electric cars, plug-in hybrids and extended-range electric vehicles become more common, coal will be fueling more and more cars. How exactly? Well, owners aren't going to have to shovel buckets of the stuff into incinerators, if that's what you're wondering.

Electric vehicles (for the most part), don't make their own electricity. They carry the energy in their charged batteries. And the batteries get their charge from a standard wall outlet, which gets its power from an electricity plant, which, in turn, gets its power from burning coal. In fact, 50 percent of all of the electricity in the United States comes from coal-fired plants [source: PBS.org]. That means that, when you go all the way down the energy chain, a lot of electric cars are actually coal-powered cars.

While coal has similar drawbacks to gasoline, it also has some benefits. On a per-mile basis, electricity from coal is a cheaper way to power a car than gasoline. Also, there's plenty of coal in the United States, so international relations shouldn't disrupt the supply too much. Also, people who get their electricity from other sources, such as hydro-electric power plants or nuclear power plants, can charge their electric cars without creating more coal emissions.

Still, the fact that some of the most anticipated clean cars heading to your local dealership will likely get their energy from a less-than-clean source just goes to show you that in the world of energy, there's no such thing as a free lunch.

For more information about alternative fuels, hybrid cars and other related topics, follow the links on the next page.

# data[].attributes.attachment_link.title
Top 10 Alternative Fuels on the Road Right Now

# data[].attributes.attachment_link.description
It happens every summer, and no one likes it. No, we're not talking about farmer's tans or your neighbor deciding that 6 a.m. is an appropriate time to mow the lawn. We're talking about the summer spike in gas prices.