 Modern natural gas hot water systems are a cost effective and efficient choice. Options exist for this fuel type to serve households of most sizes and levels of demand. |  Electric systems are inefficient and relatively expensive to run. For this reason they are generally only favoured these days where no alternative is possible. |
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 Solar boosted systems are solar-based systems that use a gas or electricity booster to maintain a sufficient temperature, regardless of how much sun there is. |  LPG (or liquid petroleum gas) is very similar to natural gas, but is more expensive to use due to the higher price of the fuel. |
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 Heat pump hot water systems extract heat from the air using a heat exchanger. These systems are popular where solar and gas aren't a realistic option. |  Home fuel cells create a lot of heat and in most cases incorporate a hot water system. HFCs are still prohibitively expensive though, and as a result are uncommon. |
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 Geothermal systems pump refrigerant through underground pipes to draw heat from the ground. While relatively cheap to run, they are expensive to install and therefore fairly uncommon. |
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