How should I set my heat pump thermostats?
Short answer
Heat pumps usually work best when they run steadily at a low flow temperature instead of blasting heat in short bursts. A common starting point is around 21°C during occupied daytime periods with only a small overnight setback, such as 19°C to 20°C. Exact settings depend on your home, comfort and system design.
Last checked 24 September 2026 · 1 source
Should I turn a heat pump off overnight?
Usually, large temperature swings are not ideal.
A heat pump is most efficient when it can maintain temperature gently. If the home is allowed to cool substantially overnight, the system may need a higher flow temperature or a long recovery period in the morning.
The installer in our source interview recommended small setbacks rather than full shutdowns.
What temperature should I use?
There is no universal number, but the interview gives a practical example:
- around 21°C during the day;
- around 19°C to 20°C overnight;
- roughly 1°C difference between floors if needed.
Those are example comfort settings, not mandatory targets.
Should every room have a different schedule?
Not necessarily.
The source installer preferred rooms to follow broadly similar schedules so the whole system operates together rather than constantly opening and closing small zones.
A heat pump generally likes a stable volume of water flowing through the heating system.
Your installer should explain how thermostatic radiator valves, room thermostats and weather compensation interact in your particular design.
What is flow temperature?
Flow temperature is the temperature of the water leaving the heat pump for the radiators or underfloor heating.
Lower flow temperatures usually improve heat-pump efficiency, provided the radiators can still release enough heat to keep the rooms comfortable.
Weather compensation can automatically vary flow temperature according to outdoor conditions.
Should the immersion heater be switched off?
For normal day-to-day heating, it should not be doing work that the heat pump can do more efficiently.
However, some systems use an immersion heater for backup or hot-water hygiene cycles. Do not disable it permanently without understanding the control strategy.
What should I do next?
If your heat pump is comfortable but expensive to run, ask the installer to review:
- flow temperature;
- weather-compensation curve;
- thermostat schedules;
- zoning;
- immersion-heater operation;
- cycling frequency.
Change one setting at a time and give the system time to settle before judging the result.
Sources
- Source interview with Heat Geek installer, thermostat and flow-temperature section.
Last checked: 24 September 2026