How much electricity does an air-source heat pump use
How to go from a home's heat demand to the electricity use of an air-to-water heat pump, using the SCOP figures on Thermia datasheets.
The consumption of an air-source heat pump is not measured by the power of the machine, but by how many kWh of electricity it needs each year to cover the home’s heat demand. The sum is simple.
The sum
SCOP tells you how many kWh of heat the heat pump delivers for each kWh of electricity it uses in a typical year. So the electricity use is the heat demand divided by the SCOP.
An illustrative example, not a measurement: a home that needs 10,000 kWh of heat a year would use about 2,500 kWh of electricity with a SCOP of 4, about 2,000 with a SCOP of 5 and about 2,860 with a SCOP of 3.5. That difference is the one between working with underfloor heating or with high-temperature radiators.
What SCOP to expect
According to the Thermia datasheets, with underfloor heating at 35 °C and an average climate, the Thermia Elve has a SCOP of 4.96 (L) and 4.89 (XL), and the iTec XTR S reaches 5.1. With radiators at 55 °C the Elve falls to 3.99 and 4.01. These are laboratory values under EN 14825: they are for comparing machines, not for promising a bill. Performance drops in winter, because the air is colder and the outdoor unit has to defrost.
What raises or lowers consumption
- The water temperature the home asks for.
- The insulation of the home, which reduces the heat demand.
- The climate. In very cold areas the annual SCOP is lower, as we explain in air-source heat pumps in extreme cold.
- Good sizing: a machine that is too big or too small works worse.
- Hot water, which also weighs on total consumption.
What you save
Compared with direct electric heating, the saving is 1 − 1/SCOP: with a SCOP of 4, 75 %. Compared with gas or oil it depends on the price of each energy and on the electricity tariff, so it is best calculated with your bills. The full logic is in how much you save with geothermal, and it applies equally to air-source.
To find out what your home would use, request the feasibility study.
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The feasibility study is free and carries no obligation. We analyse the building, the ground and the heating and cooling needs.