Resources / Heat pumps
Heat Pump Running Costs Too High? What Can I Do?
A practical guide for Devon and Cornwall homeowners whose heat pump bills are higher than expected — usual causes, what to check, and what is realistic to fix.
Quick Answer
High running costs are usually caused by design or setup issues, not by heat pumps being “expensive by nature.” The most common culprits are high flow temperatures, undersized emitters, weak fabric, the wrong electricity tariff, or a unit sized for a different standard of building than you actually have.
Some of these can be improved without major work. Others point to a design problem that should have been fixed at install. Baseline ranges: heat pump running costs explained.
View printable checklist Planning aid — not a quote
Common reasons costs run high
1. Flow temperature set too high
Heat pumps are most efficient at lower water temperatures — often around 35–45°C for space heating when emitters allow. If the system runs at 50–55°C+ to “make it feel like gas,” efficiency drops and the electricity bill rises. This is one of the most frequent and fixable issues.
Deep dive: flow temperature and efficiency.
2. Emitters that cannot deliver heat at low temperature
Small radiators sized for a hot boiler often cannot heat rooms at heat-pump temperatures. The system then compensates by raising flow temperature or running longer. Larger radiators or underfloor heating are the proper fix — not permanently hot flow temps.
Do I need to upgrade my radiators? · UFH vs radiators · HP + UFH worth it?
3. Undersized heat pump
If the unit was sized optimistically — or to a fabric standard the house never met — it will work harder and longer in cold weather. Undersizing is one of the most common installation problems and is hard to fix cheaply after the fact.
What size heat pump · heat loss calculations · not heating properly.
4. Fabric of the building
An uninsulated loft, single glazing, high air leakage or solid walls with no improvement all increase heat demand. The heat pump then has to deliver more energy every day. In older South West homes this is often the real driver of high bills.
Heat pumps in older homes · whole-house retrofit sequence.
5. Wrong electricity tariff
Running a heat pump on a standard variable rate is usually more expensive than a heat-pump-friendly or time-of-use tariff. Switching tariff can make a noticeable difference without changing the hardware. It will not fix an undersized or poorly commissioned system on its own.
See tariff discussion in running costs explained.
6. Controls and how the system is used
On/off setbacks, short cycling, disabled weather compensation, or fighting the system with manual overrides all hurt efficiency. Heat pumps prefer steady, weather-compensated operation more than sharp daily peaks — especially with underfloor heating or solid walls.
What to check first
- What flow temperature is the system actually running at for space heating?
- Are radiators (or floors) balanced and able to heat every room at that flow temperature?
- Is weather compensation enabled and commissioned for your house?
- What electricity tariff and unit rate are you on?
- Was a room-by-room heat loss done — and does the outdoor unit capacity match design conditions?
- Loft insulation, obvious draughts, and any rooms that never catch up
If rooms are cold as well as expensive, read why is my heat pump not heating the house properly in parallel. Use the heat pump readiness checklist to structure a call with an installer or assessor.
What you can realistically improve
| Issue | Typical fix path | Difficulty |
|---|---|---|
| High flow temperature | Commission curve; upgrade weak emitters if needed | Often moderate |
| Wrong tariff | Switch to a suitable heat-pump / TOU tariff | Usually easy |
| Controls / setbacks | Steady setpoints; enable weather compensation | Easy to moderate |
| Loft / draughts | Insulate and seal where practical | Moderate |
| Small radiators | Upsize emitters room by room | Cost varies |
| Undersized outdoor unit | Independent assessment; sometimes replacement | Hard / expensive |
Cheap wins first: tariff, controls, flow temperature, loft. Expensive guesses last: replacing the outdoor unit without evidence.
Tariffs matter more than people expect
Electricity unit rates on a standard tariff can make even a decent SCOP look expensive next to gas. A dedicated heat-pump or time-of-use tariff can cut the unit rate significantly for the hours the system needs most energy.
It is worth checking what you are on — and what is available for your meter and region — before assuming the hardware is the whole problem. Tariff alone will not rescue a system that must run at 55°C all winter because the radiators are too small.
Compare fossil vs heat pump framing: heat pump vs gas / oil running costs. Install cost context: heat pump costs 2026.
What “normal” looks like
In a reasonably prepared house with a well-designed system, annual space-heating costs with a heat pump are often in a similar band to modern gas — sometimes better, sometimes a little higher depending on tariff, weather and how the house is used. Oil and LPG are usually easier to beat.
If your bills are clearly above that band, something is usually wrong with design, setup or fabric — not with the idea of heat pumps in general. Typical ranges and drivers: Heat Pump Running Costs Explained.
Can solar or a battery fix high bills?
Solar reduces imported electricity and can help, especially if generation coincides with daytime demand. A battery can shift solar into evening use. Neither fixes a badly designed or poorly controlled heat pump on its own — and winter heating still draws from the grid on most homes.
Solar before or after a heat pump · is a battery worth it? · combined stack · solar payback.
Honest bottom line
High heat pump bills are a diagnosis problem. Start with flow temperature, emitters, tariff, controls and fabric. Only then consider whether the outdoor unit itself is the wrong size.
Independent assessment beats another sales visit. Fix the cause you can measure — not the brand on the case.
Frequently asked questions
Should I turn the heat pump off when I go out?
Usually no. Long setbacks force harder recovery. Steady, weather-compensated operation is typically more efficient in a heat-pump home, especially with underfloor heating or high-mass walls.
Will a new heat pump fix high bills?
Not if the real problem is emitters, fabric or controls. Replacing the outdoor unit without fixing those often repeats the same result. Diagnose first.
Can solar fix high running costs?
Solar reduces imported electricity and can help. It does not fix a badly designed or poorly controlled system on its own.
Who should I call if I suspect a design problem?
Start with the original installer if they are MCS-certified and still trading. If that is not an option, an independent assessment of heat loss, flow temperatures and emitter sizing is more useful than another sales visit.
Is my house just “too old” for a heat pump?
Older South West homes can work well when designed honestly. High bills usually mean the design or fabric path was skipped — see what works in older homes.
Next step
Get a realistic planning band for your home, then use the checklist when you speak to installers.