Like many “green” technologies, heat pumps are nothing new, but it is true to say that their popularity has increased dramatically in recent years.
You already have a heat pump, maybe more than one, in your house. A domestic fridge uses the heat pump principle to move heat into your kitchen, from the fridge, reducing the temperature inside, and warming the room, slightly.
Air Source Heat Pumps (ASHP) work on exactly the same principle as your fridge, just on a different scale, moving heat from the outside air into your house for heating water and the rooms. Heat pumps consume electricity, but they produce more watts of heat than they consume, so the efficiency is greater than 100%. This is usually expressed as Coefficient Of Performance (COP) and typical values are 2-3 for ASHP (3-4 for GSHP).
If you want to save carbon, you should really use electricity that has been generated in a sustainable way – e.g our special Greenenergy tariff, otherwise the high CO2 emissions from electricity generation and distribution losses are not offset by the ASHP.
Unlike ground source you don’t need quite a large area of land, so installation is simpler and cheaper. Performance is not as good, but the recent EST research has shown that well installed systems can achieve quite reasonable COP and payback periods are better than for ground source.
Carbon savings, relative to oil, are reasonable, though if you had access to gas it would be difficult to make the case for ASHP.