How significant are the energy bill savings that can be made from installing an air source heat pump in the place of a gas boiler? The savings on energy bills from installing an ASHP to replace a gas boiler can, on average, be very significant, in the region of 20-50 per cent, depending on variables such as insulation, system efficiency and usage pattern. They are around 300 per cent more efficient than gas boilers, with many old systems operating at well below 85 per cent, having a coefficient of performance (COP) of 3 or more – that is, they can produce, on average, three units of heat for every unit of electricity. Such savings are boosted, in turn, by low running costs and government incentives.