Common reasons and practical things you can do.
If your heat pump isn’t keeping your home warm enough, it can be frustrating. In many cases, the issue isn’t that the heat pump is faulty — it’s usually related to how the system was designed, how the house performs, or how the system is being used.
This is the most common cause. If your home loses heat quickly through walls, windows, loft, or draughts, even a correctly sized heat pump will struggle. Improving insulation often makes a bigger difference than anything else.
If the heat pump is too small for the heat loss of your property, it simply won’t be able to keep up on colder days. This usually comes down to an inaccurate or missing heat loss calculation during the design stage.
Heat pumps work best at lower water temperatures. If your radiators or underfloor heating weren’t designed for these lower temperatures, the system may not be able to deliver enough heat.
If the system is set to run at higher temperatures than necessary, or if the controls (such as weather compensation) aren’t set up correctly, performance can suffer.
Even a well-designed system can underperform if it wasn’t installed or commissioned properly. This can include things like incorrect settings, air in the system, or poor pipework insulation.
Focus on loft insulation, draught proofing, and any accessible wall or floor insulation. This is often the highest-impact improvement you can make.
Ask an experienced heat pump installer to carry out a heat loss calculation and full system check. Guessing usually leads to the wrong fix.
Make sure the system is set to run steadily rather than being turned up and down frequently. Also check that weather compensation is set correctly.
If basic checks don’t resolve the issue, get a qualified heat pump engineer to inspect the system. Many problems are fixable without replacing the whole unit.
Use our Heat Pump Estimator to better understand what size system your home actually needs.