Why is my heat pump using so much electricity? Seven checks to make

What to know first

This summary separates normal increases from settings or faults that may need investigation.

A large electricity bill does not automatically mean the heat pump is faulty. The cause is usually the electricity price, colder weather or higher demand, inefficient settings, or a design or equipment problem.

There is no single normal daily figure for every home. Heat loss, indoor temperature, hot-water use, weather and system design all matter. Compare your use in similar conditions and check it against any estimate in the installation documents.

Seven checks to make, in order

This table is a starting point, not a diagnosis.

The table draws on current Ofgem rates, Energy Saving Trust operating information, MCS performance guidance and the 2026 monitored-installation findings.

1. Separate electricity price from electricity use

Check kilowatt-hours, shown as kWh on the bill, smart-meter display or supplier account. Compare the same number of days and use actual readings where possible. A Direct Debit amount is a payment arrangement and should not be treated as a precise measure of that month’s consumption.

As checked on 27 August 2026, Ofgem’s average Direct Debit electricity rate is 26.11p/kWh in England, Scotland and Wales from 1 July to 30 September 2026. The announced average for 1 October to 31 December is 26.32p/kWh. Your rate varies by region, tariff and payment method.

If a heat pump replaced gas or oil, compare total heating expenditure rather than electricity alone. The heating load has moved onto the electricity meter, while use of the previous fuel should fall.

Good to know

Ofgem’s figures cover England, Scotland and Wales. Northern Ireland has a separate market; Power NI’s regulated domestic electricity tariff rose by 6.2% on 1 July 2026.

2. Allow for cold weather and normal defrosting

A colder home loses heat faster, so the heat pump must deliver more heat. An air source unit also has to work across a larger difference between the outside temperature and the required heating-water temperature. Compare days with similar outdoor temperatures, room settings and occupancy.

A seven-day record of daily kWh, outdoor temperature, indoor setpoint and hot-water boosts is a useful starting point. It is an evidence-gathering step, not an official performance test.

Air source heat pumps periodically run a defrost cycle to clear ice from the outdoor heat exchanger. Defrosting is normal. Ice that does not clear, repeated warnings or lost heating should be checked. Keep leaves, bins and other obstructions away from the unit so air can circulate.

3. Check whether the home is asking for more heat

Higher use can reflect higher demand rather than poor efficiency. Causes include a higher thermostat setting, longer occupied hours, more hot water, open windows or heating rooms that were previously cooler.

If the heat pump now keeps more of the home warm for longer than the old boiler did, the comparison is not like for like. Record any change in comfort, occupancy or heated floor area before concluding that the equipment is at fault.

4. Look for backup heating or an immersion heater

Many systems have a direct electric element for hot water, emergency operation or additional heat. Controller labels vary, but they may include “boost”, “backup”, “auxiliary”, “immersion” or “comfort”.

Occasional additional heating in unusually cold conditions may be expected. Regular or prolonged use needs checking. Use the manual or app to find its status and ask the installer what activates it. Do not change protected settings at random.

5. Review the hot-water schedule

Hot water needs a higher temperature than space heating and can form a significant share of electricity use. Check for an always-on immersion heater, repeated boosts, a changed schedule or a sterilisation cycle running more often than designed. The 2026 monitored-installation research found substantial differences in hot-water efficiency according to cylinder and commissioning configuration.

The sterilisation or hygiene cycle raises the cylinder temperature to control bacteria. Do not disable it or lower safety settings without following the manufacturer’s instructions or speaking to a competent installer.

Good to know

A time-of-use tariff only helps when the schedule matches its cheaper periods. Heating water during an expensive window can raise the bill even if total kWh changes little.

6. Check flow temperature, weather compensation and controls

Flow temperature is the temperature of water leaving the heat pump for radiators or underfloor heating. Lower flow temperatures normally improve efficiency, but the water must still be warm enough for the home and its heat emitters.

Weather compensation changes the flow temperature with outdoor conditions: cooler in mild weather and hotter when it is cold. A fixed high setting can produce hotter water than the home needs for much of the year, increasing the electricity used for each unit of heat.

Research commissioned by the Committee on Fuel Poverty and published on 1 July 2026 found that “the correct commissioning of weather compensation was consistently identified as the factor most strongly associated with high efficiency.”

Do not copy a setting from another home. The right one depends on the heat-loss calculation, radiator or underfloor-heating design and control strategy. If rooms only become comfortable after a large increase, ask the installer to check the heating curve, emitter sizing and system balance.

Some third-party thermostats, including “smart” products in simple on/off mode, can override the heat pump’s modulating controls and cause cycling. That does not make every smart thermostat unsuitable. The installer should confirm that the controller is compatible and allows weather compensation to operate.

Expert insight

“High demand and poor efficiency are different problems. Cold weather or open windows raise the heat needed; a high fixed flow temperature can raise the electricity needed for each unit of heat. Consider usage, comfort, weather and controls together.”

Giles Crosse

Energy Editor

Experienced editor, journalist and communications consultant specialising in consumer energy and low carbon technologies.

• Editor and campaign author for Shell, EDF Energy and Good Energy.
• Consultant to the United Nations and contributor to the World Economic Forum.
• Journalist for Reuters, the BBC, The Economist and The Guardian.

More about Giles Crosse

7. Compare the result with the design and fault log

MCS is the certification scheme covering small-scale low-carbon installations. Where supplied, find the handover pack, heat-loss calculation, proposed flow temperature and annual electricity estimate.

MCS 031:2025 includes a performance-estimate format with high and low electricity-consumption figures. Older installations may have different documents, and the estimate is not a detailed diagnosis of current performance.

MCS warns: “For these reasons your estimate is given as guidance only and should not be considered as a guarantee.” Weather, occupancy, room settings, hot-water use and ventilation can move actual consumption away from it.

Warning signs include recurring errors, frequent backup operation, repeated cycling, poor comfort despite high use, or a sudden change without a matching weather or household change. Causes may sit in the heating system rather than the outdoor unit, including pumps, valves, filters, sludge, sensors, controls or undersized emitters.

When should you call the installer?

Contact the installer promptly if the system cannot maintain heat, the outdoor unit stays heavily iced, warnings return or backup heating runs frequently. For a non-urgent complaint, provide dates, daily kWh, outdoor temperatures, room settings, hot-water schedules, controller photographs and fault-log entries. Energy Saving Trust advises checking recurring fault messages and speaking to the installer and manufacturer.

Ask for specific checks. These may include weather compensation, design flow temperature, backup-heater run time, hot-water settings, thermostat compatibility, emitter output, system flow, filters, valves, sensors and commissioning records.

If a landlord, housing provider, freeholder or managing agent arranged the work, use its repairs or complaints process. Citizens Advice says the appropriate route depends on who arranged the improvement and the household’s tenure.

For an MCS-certified installation, complain to the installer first. MCS says it may be able to help after no response for 14 days, or following an unsatisfactory outcome, subject to its scope and other conditions.

Complaint routes can depend on the MCS scheme version that applied when the work was done. The phased transition to the redeveloped MCS:2025 installer scheme runs until 31 March 2027.

Key takeaways

• Check kWh before assuming a higher bill means higher consumption.

• Compare days with similar weather, settings and occupancy.

• Brief defrosting is normal; persistent ice or repeated warnings are not.

• Check hot-water boosts, immersion use and backup-heater run time.

• High fixed flow temperatures and control conflicts can waste electricity.

• Use the design estimate as a benchmark, not a guarantee.

• Escalate persistent high use with poor comfort, faults or frequent backup.

Frequently asked questions