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How an Electric Fan Heater Works
An electric heater works by converting electrical energy into heat energy. It does this by passing heat through a metal filament with high electrical resistance. When electricity passes through resistant materials, energy is lost and converted to heat. In an electric heater, an air duct allows surrounding air to be heated by this filament.
In an electric fan heater, an added step is taken – air is pumped into and out of the heater by the action of a fan. This ensures that the air next to the filament is always cool and maximizes the heating effect.
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Energy Efficient Heaters
Many manufacturers claim that their electric heaters are 100% efficient but this is misleading – all electric heaters, with the marginal exception of electric wall fan heaters, are 100% efficient. This is due to the principle of the conservation of energy. Energy cannot be created or destroyed, only converted to new forms of energy. Any energy that does not exit the filament is converted to heat, therefore, all electric filaments are 100% efficient as heat generators.
Electric wall fan heaters differ slightly because a small amount of energy is also used to drive the fan. This energy is converted to kinetic or mechanical energy rather than heat energy. Electrical wall fan heaters are therefore not 100% – however, they are actually more effective than standard heaters.
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Energy Savings From Fan Heaters
The reason that fan heaters are more effective despite being less energy efficient is because the majority of heat transfer in air is through convection rather than conduction. Stagnant air does not transfer heat very well.
By forcing air through the fan, the thermal resistivity of the air is reduced and the flow of heat from the filament to the air is increased. The speed with which the room in which the fan heater is placed can be heated is also increased due to the faster movement of air. Also, the fact that hot air is not allowed to collect around the heater means that thermostat readings on the heater are more accurate, allowing the heater to regulate itself more effectively and turn itself off when no further heat is required. All of these factors lead to energy savings when compared to non fan-assisted electrical heaters.
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Save Money with a Gas Boiler
That isn’t to say that, however, that an electric wall fan heater is entirely eco-friendly. With 2010 gas prices at a high, most homeowners will still save more money with an efficient gas boiler compared to an electric fan heater. This is because, although an electric heater itself may be 100% efficient, the power station that produces the electricity generally won’t be.
In fact, unless a household gets its electricity from renewable energy sources, powering an electric fan heater may actually burn more fossil fuels than heating a home by gas. Power stations which generate electricity from fossil fuels are generally only 35%-40% efficient – compare that with up to 90% efficiency of a new gas boiler.
British Gas tariffs, for example, from April 9th, advertised gas at $0.14/kWh and electricity at $0.33/kWh. If an electrical heater is 100% efficient and a boiler is around 80% efficient, that still leaves the electrical heater as being around twice as expensive in terms of pure heat energy conversion.
These figures can of course be misleading - as already discussed, energy conversion is not the only factor that matters and significant energy savings can be made by ensuring that a steady flow of air is maintained. Heat pumps, when used in conjunction with an electric fan heater, can increase the effectiveness of a heating system and reduce energy costs. However, in pure energy terms, burning gas is a cheaper, greener alternative for producing heat energy.
Therefore, while electric wall fan heaters may be superior to other electric heaters, they are no more eco-friendly than burning gas in the home and are often considerably more expensive to run. As gas prices rise, it may become more cost-effective to run electrical fan heaters. Equally, as more national power is generated from renewable sources, it may become more eco-friendly to do so. However, in the current economic climate, gas central heating systems are greener and more cost-effective than electrical fan heaters.
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British Gas, “Standard Gas an Electricity” http://www.britishgas.co.uk/products-and-services/energy/our-products/standard.html
Defra, “Boiler efficiency database”, http://www.sedbuk.com/
Green Energy Efficient Homes, “Do energy efficient electric heaters really exist?” http://www.green-energy-efficient-homes.com/energy-efficient-electric-heaters.html