How Much Money can a Heat Pump Save?
The efficiency of a heat pump is affected by two external factors, the temperature you want to heat your radiators up to and the temperature of the air outside. As it gets colder outside there is less heat to capture so the unit has to work harder.
Efficiency and COP
Heat pumps use electrical energy to capture renewable heat from the air in the garden, typically you can capture 2 kWs of energy for every 1 kW of electrical energy. This means you get 3kW of heat for only 1kW of electrical input making the unit 300% efficient.
To avoid confusion we don’t use % efficiency with heat pumps, we use a different measure called Coefficient of performance. COP is just efficiency divided by 100. So 300% efficient = a COP of 3.00.
Below is a graph showing how the efficiency of the units is affected. Note how the efficiency falls as it gets colder outside and also as you raise the water temperature.