The Carbon Emission Reduction Target (CERT), approved by the Department of Energy and Climate Change (DECC) have released figures showing the cost per kilowatt of energy for the various ways of heating your home.
The below chart shows the costs:
An air source heat pump efficiency of 3:1 and ground source of 3.5:1
To view this information on the Energy Saving Trust page, click here
Electricity, not on this chart, is the most expensive form of heating. This ranges from 9.08p (economy 7) through to 15.32p for standard rate.
The reason why air and ground source heat pumps are the cheapest is because their efficiency is a multiple of the energy used.
To explain this we can use the example of gas, which is normally around 80%. When 1kW worth of gas is burnt to heat your home, around 20% is lost due to inefficiencies within the boiler. Examples include a less than perfect fuel mix and inefficiencies within the heat exchanger.
The same can be said of LPG and oil burners. In fact it is only electric heaters which operate at 100% efficiency – all the electricity is used to create heat, none is lost as a by-product.
Air and ground source heat pumps take their energy from the atmosphere; either the air temperate or ground temperature. They are therefore taking more energy than they are using. In the case of an air source heat pump they need 1kW of electricity to take 3kW of energy from the atmosphere. So the cost of energy is 1/3 of the electricity used to generate that energy.