How much does an air source heat pump cost to run?

An air source heat pump can cost less or more to run than an existing heating system. The result depends on the heat your home needs, the electricity tariff you pay and how efficiently the system delivers that heat. A well-designed installation uses electricity steadily at a relatively low flow temperature. A poorly matched system may need more electricity and cost more than expected.

The most useful estimate comes from the building rather than a typical household figure. We calculate the heat loss room by room, assess the hot water requirement and model the proposed heat pump at the temperatures your home needs. That gives us an estimate of annual electricity use, which we can then compare with your current oil, LPG, gas or direct-electric heating costs.

The main running-cost factors are:

• Heat demand: a large, poorly insulated house needs more heat than a smaller, well-insulated one. The heat pump’s electricity use rises with the amount of heat it must produce.
• Flow temperature: the lower the temperature of the water circulating through the radiators or underfloor heating, the more efficiently the heat pump generally operates. Larger radiators or improved insulation can help the system work at a lower temperature.
• Electricity tariff: the price charged for each unit of electricity has a direct effect on the bill. We use the tariff you are considering when discussing likely costs rather than assuming every household pays the same rate.
• Controls and operation: weather compensation, correct room temperatures and a steady heating pattern can reduce unnecessary high-temperature operation. Frequent changes to the controls can make the system work harder.
• Hot water: heating a cylinder requires the system to operate at a higher temperature than space heating. The timing of hot-water heating and any supplementary heating element affects electricity use.
• Cold weather: the heat pump works harder when outdoor temperatures fall. It may also need to defrost its outdoor unit, which uses some electricity. The system design must allow for these conditions.

Electricity use is not the same as heat output. A heat pump moves heat from outside air into the property rather than creating all the heat from electricity. Its efficiency varies with the outdoor temperature and the temperature required by the heating system. For that reason, a quoted seasonal efficiency figure is more useful than a single best-case efficiency figure.

Your expected cost should therefore be based on the system’s annual electricity consumption, multiplied by the electricity unit rate, with the normal electricity standing charge considered separately. The standing charge applies to the property’s electricity supply whether or not the heat pump is running, so it should not be treated as a heat-pump cost alone.

Older homes need a careful assessment. A solid-wall house, barn conversion or listed property may have higher heat loss than a modern insulated home. That does not automatically rule out an air source heat pump, but it can affect the size of the system, the radiator design and the expected electricity use. We look at the construction, insulation, windows, draughts and existing heat emitters before drawing conclusions about running costs.

Some existing radiators may be large enough to heat the rooms at the lower flow temperatures a heat pump prefers. Others may need replacing or supplementing. If the system has to run at a higher temperature to compensate for undersized radiators, its electricity consumption may increase. We include radiator and pipework changes in the design discussion instead of treating them as an afterthought.

Properties currently using oil or LPG need a like-for-like comparison. We compare the estimated electricity requirement with the fuel consumption and current price for the existing system. That comparison should include the practical factors that affect the decision, such as fuel deliveries, cylinder or tank arrangements and any required electrical work. We do not assume that changing the heat source will produce a saving in every property.

For a home using direct electric heaters, the comparison may be different because direct electric heating turns each unit of electricity into heat at the point of use, while a heat pump can move heat from outside. The heat pump still needs a suitable design and sufficient electrical capacity, and the result depends on the property’s heat demand and tariff.

Solar panels can change when you buy electricity from the grid. If a heat pump operates during periods when solar electricity is being generated, some of its demand may be supplied on site. A battery can store some surplus electricity for later use. The value depends on the system size, household demand, controls, export arrangements and when the heating and hot water are scheduled.

Solar generation should not be counted as free heat in every running-cost estimate. Winter heat demand is often highest when solar generation is lower, and the heat pump will still draw electricity from the grid at other times. We can model solar and battery use alongside the heating system so the figures reflect the whole installation rather than an idealised example.

The controls affect the bill as much as the equipment’s specification. Weather compensation adjusts the heating water temperature to suit outdoor conditions. A correctly set system can maintain comfortable room temperatures without repeatedly driving the heat pump to a high flow temperature. Hot water schedules, immersion-heater settings and any backup heating also need to be understood before judging performance.

During handover, we explain the controls and the difference between space heating and hot-water settings. If the property feels cold, the electricity use seems unexpectedly high or the system is relying heavily on backup heating, the settings and operating pattern should be checked before assuming the heat pump itself is at fault.

A reliable running-cost estimate should show its assumptions. We can explain the heat-loss calculation, the proposed flow temperatures, the estimated annual electricity use and the tariff used for the comparison. We also discuss which radiator, insulation or electrical changes have been included. That gives you a way to test the estimate against your own bills and priorities.

The installation is designed by our in-house heating and electrical team, so the heat pump, radiator and pipework changes and associated electrical work are considered together. MCS certification also means we can make an eligible Boiler Upgrade Scheme grant application on your behalf and install systems that can qualify for the Smart Export Guarantee where solar or battery storage is included. The grant and export arrangements affect the overall financial calculation, but they do not change the heat pump’s underlying electricity consumption.

Running costs should be reviewed alongside installation cost, maintenance, tariff changes and the condition of the existing heating system. We give you the property-specific information needed to decide whether an air source heat pump fits your home, rather than presenting a generic saving that may not apply to it.