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Central Heat

Furnaces

The majority of North American households depend on a central furnace to provide heat. A furnace works by blowing heated air through ducts that deliver the warm air to rooms throughout the house via air registers or grills. This type of heating system is called a ducted warm-air or forced warm-air distribution system. It can be powered by electricity, natural gas, or fuel oil.

Inside a gas- or oil-fired furnace, the fuel is mixed with air and burned. The flames heat a metal heat exchanger where the heat is transferred to air. Air is pushed through the heat exchanger by the "air handler's" furnace fan and then forced through the ductwork downstream of the heat exchanger. At the furnace, combustion products are vented out of the building through a flue pipe. Older "atmospheric" furnaces vented directly to the atmosphere, and wasted about 30% of the fuel energy just to keep the exhaust hot enough to safely rise through the chimney. Current minimum-efficiency furnaces reduce this waste substantially by using an "inducer" fan to pull the exhaust gases through the heat exchanger and induce draft in the chimney. "Condensing" furnaces are designed to reclaim much of this escaping heat by cooling exhaust gases well below 140°F, where water vapor in the exhaust condenses into water. This is the primary feature of a high-efficiency furnace (or boiler). These typically vent through a sidewall with a plastic pipe.

New furnace standards are currently under development by the U.S. Department of Energy, and are due to be finalized in the spring of 2016. The current furnace standards have not been updated since 1987.

Heating system controls regulate when the various components of the heating system turn on and off. The most important control from your standpoint is the thermostat, which turns the system - or at least the distribution system - on and off to keep you comfortable. A typical forced air system will have a single thermostat. But, there are other internal controls in a heating system, such as "high limit" switches that are part of an invisible but critical set of safety controls.

The best gas furnaces and boilers today have efficiencies over 90%

The efficiency of a fossil-fuel furnace or boiler is a measure of the amount of useful heat produced per unit of input energy (fuel). Combustion efficiency is the simplest measure; it is just the system's efficiency while it is running. Combustion efficiency is like the miles per gallon your car gets cruising along at 55 miles per hour on the highway.

In the U.S., furnace efficiency is regulated by minimum AFUE (Annual Fuel Utilization Efficiency). AFUE estimates seasonal efficiency, averaging peak and part-load situations. AFUE accounts for start-up, cool-down, and other operating losses that occur in real operating conditions, and includes an estimate of electricity used by the air handler, inducer fan, and controls. AFUE is like your car mileage between fill-ups, including both highway driving and stop-and-go traffic. The higher the AFUE, the more efficient the furnace or boiler.

Boilers

Boilers are special-purpose water heaters. While furnaces carry heat in warm air, boiler systems distribute the heat in hot water, which gives up heat as it passes through radiators or other devices in rooms throughout the house. The cooler water then returns to the boiler to be reheated. Hot water systems are often called hydronic systems. Residential boilers generally use natural gas or heating oil for fuel.

In steam boilers, which are much less common in homes today, the water is boiled and steam carries heat through the house, condensing to water in the radiators as it cools. Oil and natural gas are commonly used.

Instead of a fan and duct system, a boiler uses a pump to circulate hot water through pipes to radiators. Some hot water systems circulate water through plastic tubing in the floor, a system called radiant floor heating (see "State of the Art Heating"). Important boiler controls include thermostats, aquastats, and valves that regulate circulation and water temperature. Although the cost is not trivial, it is generally much easier to install "zone" thermostats and controls for individual rooms with a hydronic system than with forced air. Some controls are standard features in new boilers, while others can be added on to save energy (see the "Modifications by Heating System Technicians" section on the heating maintenance page).

As with furnaces, condensing gas-fired boilers are relatively common, and significantly more efficient than non-condensing boilers (unless very sophisticated controls are employed). Oil-fired condensing boilers are uncommon in the U.S. for several reasons related to lower latent heat potential, and potential for greater fouling with conventional fuel oil.

Heat Pumps

Heat pumps are just two-way air conditioners (see detailed description in the cooling systems section). During the summer, an air conditioner works by moving heat from the relatively cool indoors to the relatively warm outside. In winter, the heat pump reverses this trick, scavenging heat from the cold outdoors with the help of an electrical system, and discharging that heat inside the house. Almost all heat pumps use forced warm-air delivery systems to move heated air throughout the house.

A ground-source heat pump heats and cools in any climate by exchanging heat with the ground, which has a more constant temperature.

There are two relatively common types of heat pumps. Air-source heat pumps use the outside air as the heat source in winter and heat sink in summer. Ground-source (also called geothermal, GeoExchange, or GX) heat pumps get their heat from underground, where temperatures are more constant year-round. Air-source heat pumps are far more common than ground-source heat pumps because they are cheaper and easier to install. Ground-source heat pumps, however, are much more efficient, and are frequently chosen by consumers who plan to remain in the same house for a long time, or have a strong desire to live more sustainably. How to determine whether a heat pump makes sense in your climate is discussed further under "Fuel Options."

Whereas an air-source heat pump is installed much like a central air conditioner, ground-source heat pumps require that a "loop" be buried in the ground, usually in long, shallow (3-6' deep) trenches or in one or more vertical boreholes. The particular method used will depend on the experience of the installer, the size of your lot, the subsoil, and the landscape. Alternatively, some systems draw in groundwater and pass it through the heat exchanger instead of using a refrigerant. The groundwater is then returned to the aquifer.

Because electricity in a heat pump is used to move heat rather than to generate it, the heat pump can deliver more energy than it consumes. The ratio of delivered heating energy to consumed energy is called the coefficient of performance, or COP, with typical values ranging from 1.5 to 3.5. This is a "steady-state" measure and not directly comparable to the heating season performance factor (HSPF), a seasonal measure mandated for rating the heating efficiency of air-source heat pumps. Converting between the measures is not straightforward, but ground-source units are generally more efficient than air-source heat pumps.

Direct Heat

Gas-Fired Space Heaters

In some areas, gas-fired direct heating equipment is popular. This includes wall-mounted, free-standing, and floor furnaces, all characterized by their lack of ductwork and relatively small heat output. Because they lack ducts, they are most useful for warming a single room. If heating several rooms is required, either the doors between rooms must be left open or another heating method is necessary. Better models use "sealed combustion air" systems, with pipes installed through the wall to both provide combustion air and carry off the combustion products. These units can provide acceptable performance, particularly for cabins and other buildings where large temperature differences between bedrooms and main rooms are acceptable. The models can be fired with natural gas or propane, and some burn kerosene.

Unvented Gas-Fired Heaters: A Bad Idea

Gas or kerosene space heaters that do not have an exhaust vent have been sold for decades, but we strongly discourage their use for health and safety reasons. Known as "vent-free" gas heating appliances by manufacturers, they include wall-mounted and free-standing heaters as well as open-flame gas fireplaces with ceramic logs that are not actually connected to a chimney. Manufacturers claim that because the products' combustion efficiency is very high, they are safe for building occupants. However, this claim is only valid if you keep a nearby window open for adequate fresh air- which defeats the purpose of supplemental heat. Dangers include exposure to combustion by-products, as discussed in Ventilation, and oxygen depletion (these heaters must be equipped with oxygen depletion sensors). Because of these hazards, at least five states (California, Minnesota, Massachusetts, Montana, and Alaska) prohibit their use in homes, and many cities in the United States and Canada have banned them as well.

Electric Space Heaters

Portable (plug-in) electric heaters are inexpensive to buy, but costly to use. These resistive heaters include "oil-filled" and "quartz-infrared" heaters. They convert electric current from the wall socket directly into heat, like a toaster or clothes iron. As explained further under "Selecting a New System," it takes a lot of electricity to deliver the same amount of useful heat that natural gas or oil can provide onsite. A 1,500- watt plug-in heater will use almost the entire capacity of a 15-amp branch circuit; thus, adding much additional load will trip the circuit breaker or blow the fuse. The cost to operate a 1,500-watt unit for an hour is simple to compute: it is 1.5 times your electricity cost in cents per kilowatt-hour. At national average rates-12¢ kWh for electricity- that heater would cost 18¢ per hour to run-and quickly cost more than its purchase price. On the other hand, for intermittent use, it is the "least-bad" solution when alternatives would require major investments to improve ductwork for a specific area, for example. Just remember, electric resistance heat is usually the most expensive form of heat, and it is, therefore, seldom recommended.

"Electric baseboard heat" is yet another kind of resistive heating, similar to a plug-in space heater except that it is hard-wired. It has two principal virtues: the installation cost is low, and it is easy to install individual room thermostats so you can turn down the heat in rooms that aren't being used. Operating costs, as for all resistive systems, are generally very high, unless the house is "super-insulated."

Wood-Burning and Pellet Stoves

Wood heating can make a great deal of sense in rural areas if you enjoy stacking wood and stoking the stove or furnace. Wood prices are generally lower than gas, oil, or electricity. If you cut your own wood, the savings can be large. Pollutants from wood burning have been a problem in some parts of the country, causing the U.S. Environmental Protection Agency (EPA) to implement regulations that govern pollution emissions from wood stoves. As a result, new models are quite clean-burning. Pellet stoves offer a number of advantages over wood stoves. They are less polluting than wood stoves and offer users greater convenience, temperature control, and indoor air quality.

Fireplaces

Gas (and most wood) fireplaces are basically part of a room's décor, providing a warm glow (and a way to dispose of secret documents), but typically not an effective heat source. With customary installations that rely on air drawn from the room into the fireplace for combustion and dilution, the fireplace will generally lose more heat than it provides, because so much warm air is drawn through the unit and must be replaced by cold outside air. On the other hand, if the fireplace is provided with a tight-sealing glass door, a source of outside air, and a good chimney damper, it can provide useful heat.

State of the Art Heating

Radiant floor heat generally refers to systems that circulate warm water in tubes under the floor. This warms the floor, which in turn warms people using the room. It is highly controllable, considered efficient by its advocates, and is expensive to install. It also requires a very experienced system designer and installer, and limits carpet choices and other floor finishes: you don't want to "blanket" your heat source.

Contact the Radiant Panel Association

Ductless, Mini-Split, Multi-Split. Residential ductwork is relatively rare outside North America. "Ductless" heat pumps, which distribute energy through refrigerant lines instead of water or air, are widely used. Large field trials in the Pacific Northwest suggest that they can have good cold weather performance, and be very cost-effective where replacing electric resistance heating. Like ground-source systems, relative immaturity of the market helps assure that whole-house multi-split systems carry premium prices.

Combined heat and power (CHP) or cogeneration for houses is being seriously studied in some countries. The basic premise is to use a small generator to meet some of the electric demand of the house, and recover the waste heat (typically more than 70% of the heating value of the fuel) to heat the house (hydronic or water-to-air systems) and make domestic hot water. These systems are not yet widely available. They are likely to have the best economics in houses with high heating bills because the house cannot be feasibly insulated, such as solid stone or brick homes.

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The majority of North American households depend on a central furnace to provide heat. A furnace works by blowing heated air through ducts that deliver the warm air to rooms throughout the house via air registers or grills. This type of heating system is called a ducted warm-air or forced warm-air distribution system.

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Upgrading Your Existing Heating System

Even if you aren't about to go out and buy a state-of-the-art, high-efficiency heating system, it is still a good idea to hire a contractor to check out your system, perform regular tune-ups, and look for opportunities to realize substantial savings by boosting the efficiency and performance of your present system. In a few situations, it makes more economic sense to tune up or modify your existing system than to replace it.

Routine Professional Tune-Ups

Oil-fired systems should be tuned up and cleaned every year, unless they operate on ultra-low sulfur fuel. Gas-fired systems should be checked every two years, and heat pumps every two or three years.

Regular tune-ups should cut heating costs, and they also increase the lifetime of the system, reduce breakdowns and repair costs, and cut the amount of carbon monoxide, smoke, and other pollutants pumped into the atmosphere by fossil-fueled systems.

The company that sells oil usually has trained technicians who can test your furnace or boiler, clean it, and tune it for optimum efficiency. Independent contractors provide this service as well. A complete tune-up may cost more than $100, but can reduce your heating bill from 3-10%. Some companies perform these services as part of a regular service contract. Check to make sure that all of the services listed below are included.

Combustion efficiency. Incomplete combustion of fuel and excessively high flue gas temperatures are the two main contributors to low efficiency. If the technician cannot get the combustion efficiency up to at least 75% after tuning it up, you should consider replacing the system. (Note that the combustion efficiency is different from annual fuel utilization efficiency or AFUE. For older burners, the AFUE can be estimated by multiplying the combustion efficiency by 0.85. Thus, if the combustion efficiency is 75%, the AFUE is around 0.75 x 0.85 = 64%.)

The technician should measure the efficiency of your system both before and after tuning it up and provide you with a copy of the results. Combustion efficiency is determined based on one or more of the following tests: 1) flue temperature; 2) percent carbon dioxide or oxygen; 3) smoke number (oil); 4) carbon monoxide; and 5) draft.

Flue temperature. High flue gas temperatures mean that a lot of heat (and money) is being lost up the chimney. Typical flue temperatures are:

Gas 300-600°F

Gas (condensing system) 100-140°F

Oil 400-600°F

Oil (flame retention burner) 300-500°F

Carbon dioxide. Carbon dioxide is the primary end product of fossil-fuel combustion. Too little carbon dioxide indicates incomplete combustion. For an oil burner, the CO2 concentration should measure between 10 and 12%. For gas, it should be between 7 and 9%. If an oxygen reading is taken instead, it should be between 3 and 6% for oil systems, or between 5 and 7% for non-condensing gas systems.

Smoke (oil only). Smoke indicates lack of complete combustion and is usually not present in gas systems. For an oil system, on a scale of 0 to 10, the smoke number should be no higher than 1.

Carbon monoxide (gas only). Carbon monoxide (CO) indicates incomplete combustion. For safety reasons, recommended CO levels in the flue gas should not exceed 400 parts per million.

Cleaning. Oil system parts to be cleaned include the burner (nozzle, electrodes, filters), combustion chamber, oil line filter, and flue pipe. For all systems, clean the heat exchanger surfaces. Oil nozzles and filters are often replaced rather than cleaned. Sediment should be removed from the boiler and steam lines; corrosion inhibitors may be added to the boiler.

Adjustments. Air- and fuel-flow adjustments will be made based on the results of efficiency testing. The internal thermostat on the furnace or boiler (fan thermostat or aquastat) should be calibrated to turn on and off at the appropriate temperatures.

Pumps and Fans. Pumps and fans should be inspected and lubricated if necessary.

Modifications by Heating System Technicians

During a routine tune-up, a heating technician may recommend additional modifications to your heating system. All of these measures for boosting the efficiency of your furnace or boiler require a professional with the proper training and tools.

Duct sealing. In homes heated with forced warm air, ducts should be inspected and sealed to ensure adequate airflow and eliminate loss of heated air. It is not uncommon for ducts to leak as much as 15-20% of the air passing through them. And, leaky ducts can bring additional dust and humidity into living spaces. Thorough duct sealing costs several hundred dollars, but can cut heating and cooling costs in many homes by 20%.

A contractor can test your ducts to determine the extent and location of leaks. Accessible ducts are often sealed using mastic, which is applied to the outside of duct joints and other leak sites. A new alternative to mastic is aerosol-based duct sealing ("Aeroseal"). A machine connected to the ductwork blows a latex aerosol throughout ducts to seal leaks from the inside. This system can reach leaks in hard to reach or inaccessible spaces and effectively seals leaks up to 1/4" in diameter.

Did You Know? About 20% of space conditioning energy is wasted through duct losses. Field studies demonstrate that aerosol-based duct sealing can reduce duct leakage by 80% on average.

Reducing System Size. If you have an older oil-fired system, and you've added insulation, upgraded your windows, or tightened your house, chances are that your burner runs for only a fraction of the time, even in the coldest weather. When your heating system constantly turns on and off, its performance is like driving in stop-and-go traffic: you don't get very good mileage. A simple way to reduce this waste is by decreasing the rate at which oil is fed into the burner. With oil systems, the service technician can install a smaller nozzle, which costs just a few dollars and can cut fuel bills by 5-10%. Nozzles are sized according to fuel-flow rates. The specification plate on your burner should include an acceptable flow range; an average range would be from 0.50 to 1.25 gallons per hour (GPH). Nozzle size should not be reduced more than 25-30% below the lowest firing range on the specification plate. Burners for steam systems should not be downsized.

Draft reduction (oil only). The draft test will determine whether excess heat is being lost up the chimney. This problem is particularly common in systems that were converted from coal to oil. If the draft is too high, your service technician should install a barometric damper in the flue pipe. This may cost from $20-100, but can reduce fuel use by 5% or more. If a barometric damper is already there, it may simply need adjustment.

New oil burner installation. If you have an old, inefficient oil burner but are not ready to replace the whole thing, have a flame-retention burner installed. It will mix oil and air more thoroughly, operate with less airflow, and send less heat up the chimney. In addition, a flame-retention burner will block airflow through the burner when the system is not running, reducing heat loss up the chimney. Flame-retention burners cost $400-600, depending on whether a new combustion chamber and controls are needed. A properly sized flame-retention burner with reduced nozzle size should save 10-20%. You'll do even better, though, replacing the whole furnace or boiler with a state-of-the art high-efficiency model.

Outdoor reset or aquastat (hot water boilers only). An aquastat regulates boiler temperatures, keeping the water within a prescribed temperature range, usually around 180°F. Unfortunately, it will keep the water just as hot even when there is little need for heat, such as during spring and fall months. A modulating aquastat (or outdoor reset) senses outdoor temperature and keeps the boiler water only as hot as needed.

Brand-name aquastats sell for $150-350 and reduce fuel consumption by 5-10%. You can control an aquastat manually as well (see the section below on operating your system). Condensing boilers without these controls will not save energy, since they will operate at temperatures where no flue gas condensing occurs. Note also that some advanced "purge" controls for non-condensing boilers show performance rivaling that of less well-controlled condensing systems.

With an outdoor reset control, the water temperature in a hot water boiler can be adjusted based on how cold it is outside.

Time delay relay (hot water boilers only). Another strategy for controlling boiler water temperature is the time delay relay. When the room thermostat signals a need for heat, water heated earlier is circulated through the radiators without the boiler turning on. If circulation of warm water is not sufficient to heat the home within a specified time, the boiler burner fires to further heat the boiler water. With a time delay relay, circulation of lower temperature boiler water can provide adequate heating during milder weather. A time delay relay can be installed by a contractor for $50-75 and yield savings of 10%.

Automatic vent damper. The automatic damper is a metal flap that closes off the flue when the burner shuts off. In practice, the electric vent damper is operated by the thermostat. In turn, opening the vent damper signals the boiler or furnace to turn on. This prevents the possibility of spilling combustion gases into the house if the damper malfunctions. Vent dampers cost from $125-400 installed and can cut fuel consumption by 3-15%. Savings are highest with steam boilers, large hot water boilers, and warm-air furnaces that are located in heated spaces, where heated room air can escape up the chimney during the off cycle. If the heating system is located in an unheated basement or if it has a flame retention oil burner, savings will probably be less than 5%. If you have an older oil burner, converting it to a flame retention type is generally a better investment (see "New oil burner installation," page 92). Caution: vent dampers are not suitable for all gas heating systems. Ask your service technician whether a vent damper is appropriate for your system.

Adjustable radiator vents and valves. To reduce heat flow to unused rooms, valves on some hot water radiators may be turned down. Valves on steam radiators should always be completely on or off, not in between. An alternative for steam radiators is to install an adjustable air vent, typically costing about $10-15 at hardware and heating supply stores. These vents are screwed onto the radiator in place of existing vents, and they control how much steam gets into the radiator to heat it up.

You can get even greater control with either steam or hot water radiators by installing thermostatic radiator valves. These valves allow you to select the temperature of each room. When the designed temperature is reached, the valve shuts the radiator off. These valves cost $50-125 each installed, and can be a less expensive way to create separate heating zones, compared to repiping the whole house.

Programmable thermostats and "climate controls." Setting the thermostat manually works well but is inconvenient. More convenient is a programmable thermostat that will turn on the heat a half-hour before your alarm goes off in the morning. Some programmable thermostats have several different set-back periods, helping you save energy when you go off to work and the kids leave for school. Programmable thermostats cost from about $40 to $150 for models that allow separate programming for each day of the week. Most will pay for themselves in about a year, if they are actually programmed properly and used consistently. This means several degrees of setback in winter and "set-up" in the air conditioning season. Unfortunately, many programmable thermostats have been hard to use, so many users have not realized the full energy savings possible with proper use. As a result, the ENERGY STAR program for programmable thermostats was suspended, but a new program for "Residential Climate Controls" is under consideration. The new program would qualify products that meet usability criteria and warrants investigation. Until that program goes into effect and there is good market availability of ENERGY STAR climate controls, ACEEE recommends shopping around for a unit with a programming interface that makes sense to you. If your utility provides a thermostat to you through a peak-load reduction or other program, make sure the installer takes the time to walk you through the instructions so you can adjust the programming to meet your needs.

Tankless coil water heaters. If domestic hot water is provided by your heating system boiler with a tankless coil, then during the summer, the boiler must operate constantly just to provide hot water for showers, washing dishes, etc. There are several ways to avoid this waste. The simplest but least convenient is to install a timer switch so that you can turn your whole heating system off at night and when you are away during the summer months. Another option is to install a stand-alone, gas-fired (or propane) water heater to use in the summer when your heating system is off. A third option is to install an indirect water heater that draws heat from the boiler (like a tankless coil), but stores the hot water so that the boiler does not need to run as frequently. This option is usually the most cost-effective alternative to tankless coils in cold climates. A fourth solution may be to buy a solar water heater. In most areas of the country, solar water heaters can provide nearly 100% of summertime hot water needs, thus complementing your wintertime boiler-produced hot water perfectly. Although this system requires a large capital investment, it is the best solution from an environmental standpoint, because solar energy produces virtually no pollutants, in contrast to fossil fuels and electricity. (See Water Heating.) If you are building a new house, but not sure if you're ready to install solar water heating from the start, there are inexpensive steps you can take to support the installation at a later date. Plan for a south-facing roof and install "rough-in" plumbing; it will be cost-prohibitive to complete these retrofits later.

Some Modifications You Can Do Yourself

You don't need to hire a contractor to take care of all the energy saving modifications. All of these modifications deal with heat distribution- getting the most heat from your furnace or boiler to the rooms in your house. These should be done regardless of the tested combustion efficiency of the heating system.

Pipe insulation. All hot water and steam pipes passing through unheated areas should be wrapped with insulation. Use specially made foam or fiberglass pipe insulation, which can cost $0.30-0.80 per foot and saves about $0.50 per foot per year. Try to use insulation with a wall thickness of at least 3⁄4" for fiberglass and 1⁄2" for foam. Do not wrap steam pipes with foam as it could melt. Older steam pipes may be wrapped with asbestos, which should not present a health hazard as long as it is well-sealed, not flaky, and not in a living space. If some of the white protective sheathing is missing, contact an asbestos abatement contractor.

Duct insulation. First, seal all duct joints and seams with mastic (a special paste) or UL-181b certified duct tape to keep hot air from leaking out of the ducts. Duct tape is that strong silver or grey tape most of us know for its other applications, such as repairing broom handles and car parts. Unfortunately, non-UL-181b duct tape will dry up and lose its adhesion over time, especially in unheated spaces. Mastic, on the other hand, spreads easily and dries permanently, and is the preferred material for sealing joints and seams in metal ductwork. (See section on "Modifications by Heating System Technicians" for more on duct sealing.)

Secondly, all hot-air ducts passing through unheated spaces should be wrapped with insulation. You can use standard foil-faced fiberglass insulation, keeping the foil facing out and visible; vinyl-faced insulation made especially for ducts; or rigid foam insulation. R-8 is recommended in cold climates. Then, seal all joints or seams in the insulation. Use UL-181b duct tape with standard fiberglass batts and rigid foam; with vinyl-faced duct insulation, use duct tape or double-over and staple the seams.

Radiator reflectors. Radiators are designed to heat the living space, but they can lose a lot of heat into the exterior walls they are installed against. You can reduce this loss by placing reflectors between the wall and the radiator. You can make reflectors from foil-covered cardboard, available from many building supply stores. The reflector should be the same size or slightly larger than the radiator. The foil should be periodically cleaned for maximum heat reflection.

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Even if you aren't about to go out and buy a state-of-the-art, high-efficiency heating system, it is still a good idea to hire a contractor to check out your system, perform regular tune-ups, and look for opportunities to realize substantial savings by boosting the efficiency and performance of your present system.

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I received an email the other day saying:
Love your site! So many ideas and very kid friendly. I am a new user and maybe it's a bit presumptuous of me to suggest content but....I'm doing 'Electricity' in science right now with my grade 5/6 class and would love to see that included in your website beyond the Ben Franklin reference. Thank you so much for providing this content.-Siobhan Lane in Kamloops, BC, Canada
My answer, at the time, should have been no - but with a name like Siobhan how could I turn her down. Turns out a few email exchanges later, I find out that she is related to half of Ireland. Shockingly (no pun intended) I also had a couple of hours free - and so I got to work. Over the next few days here's what I put together for her and her 5/6 Grade Class in BC:

Learn about Electricity:

Electricity is a very useful form of energy. Electricity can be used to perform work such as:
But where do these items get their electricity?

Heating our homes or our food (electrical energy is converted into light and heat energy)

Lighting our lamps (electrical energy is converted into light and heat energy)

Powering our computers (electrical energy is converted into light, heat and sound energy) or

Powering a motor (electrical energy is converted into movement, heat and sound energy).

All appliances, whether small or large, need a power source.

What is a power source?

A power source provides a steady flow of electrons. Larger appliances like heaters and large computers usually get their power from the mains. But small batteries (cells) can also be a power source. The problem with electrical energy obtained from battery power though, is that battery power eventually runs out and the battery has to be thrown away or recharged. On the other hand, electricity flowing from a mains doesn't run out is much more powerful (and dangerous so be careful!).

Electricity is a "secondary" source of energy. In other words other sources of energy are needed to produce electricity.

What is an electrical circuit?

Electrical current needs a PATH on which to travel. Another name for this path is a circuit. Electricity flows from the power source, in a loop or a circuit, back to the power source. This means that the electricity must start and finish at the same power source. If the circuit is not complete (i.e. if the loop is not closed) then electricity cannot flow through it properly.

Which one of these loops allows electricity to flow?

LOOP1 or LOOP2? Explain your answer.

LOOP 1:

LOOP 2:

Electricity flowing through a circuit is called a current.

A load is a device that uses electricity (like a buzzer of a light blub). The load needs electrical energy to be able work.

The electric current from the power source flows from one place to another through the wire of a circuit.

Conductors and Insulators:

These metal wires ( conductors) are often wrapped in plastic ( insulators) so as to stop the electric current flowing into objects that touch the wire.

If electricity flows through an object, then scientists say the object conducts electricity, and they call it a conductor. Metals are very good conductors. A small bit of energy is released as heat when electricity flows through the conductor.
Here's an experiment you can do at home to test if different materials are insulators or conductors.
If electricity doesn't flow through an object then scientists call it an insulator. Plastic, wood and rubber are all very good insulators.

You can increase a circuit by increasing the length of the connecting wire. What do you think will happen to the light bulb as the wire gets longer? How about as the wire gets shorter?

What is a switch?
Here are some instructions to help you do some science at home and make your own switch.
Switches allow you control over the circuit. You can stop the flow of electricity by breaking the circuit. When the switch is in the "on" position the circuit is complete. When the switch is "off" position the circuit is broken.

How do I draw a circuit?

Sometimes circuits are drawn using special symbols. These symbols make it faster and easier to draw circuits and once you understand what the different symbols stand for, these diagrams are very easy to understand. However if you don't understand what the different symbols stand for, then the diagrams look a little strange!

Here is a chart to help you to understand the different circuit symbols that are used in when drawing the different components of the circuit. Each circuit component has it's own symbol. These symbols are universal so we call all understand each other's diagrams.

"In Series" or "In Parallel" Circuits:

Whenever two components are joined together in the same circuit, there are two different ways they can be wired: in series or in parallel.

In the in series circuit the components are joined together in one bigger circuit i.e. one continuous loop. Electricity passes first through one component first then the next one. A disadvantage of the in series circuit is that when one component malfunctions, the other components will stop working.

Another option would be to make two SMALLER circuits with each bulb having it's OWN circuit parallel to one other. A major advantage of parallel circuits is that if one component malfunctions, the other continues to function.

The diagram below shows the difference between these two types of circuits.

Batteries can also be connected in parallel or in series. But, if you are using more than one battery in a circuit they need to all face in the same direction to work. If two batteries are connected in series, then the voltages add together.

Adding more cells in a line (in series) will make the blub burn brighter.

What do you think would happen if you add too many cells in the series?

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I received an email the other day saying: Love your site! So many ideas and very kid friendly. I am a new user and maybe it's a bit presumptuous of me to suggest content but....I'm doing 'Electricity' in science right now with my grade 5/6 class and would love to see that included in your website beyond the Ben Franklin reference.

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Exercise per Paolo

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Types of Energy Anchor Chart - Use this mini anchor chart to help teach Science TEK 4.6A. Help your students remember the difference between mechanical, electrical, light, thermal, and sound energy.