How do I know if my Cosy heat pump is running OK?

Q: How do I know if my Cosy heat pump is running OK?

Look at a week, not a day. A healthy heat pump keeps the rooms at the temperature you set, runs in long steady stretches, and gives out several times more heat than the electricity it uses. Judge all three against the weather and your own past weeks.

Updated 29 September 2026

Short answer: look at a week, not a day. A healthy heat pump keeps the rooms at the temperature you set, runs in long steady stretches, and gives out several times more heat than the electricity it uses. Judge all three against the weather and your own past weeks.

A single cold day always looks worse than a mild one, so one bad-looking day tells you very little. What matters is whether this week is in line with past weeks that had similar weather.

Good signs

The rooms reach the temperature you set, and stay there.
It runs for long stretches at low power in cold weather.
Heat out is well above electricity in, day after day.
The hot water is ready when you need it.

Worth a look

It switches on and off every few minutes (called short-cycling).
Efficiency drops compared with past weeks of similar weather.
Rooms stay cold even when it runs hard.
Lots of use falls in the 4pm to 7pm peak.

In Snugdays: Trends sets each day against what this home usually does in that weather, and Advice flags short-cycling or a drop before it shows on your bill.