Heat Pump Problems
An honest look at what goes wrong, and how to avoid it.
We install heat pumps for a living, so we see what happens when they're done right and when they're done badly. Most complaints about heat pumps trace back to the installation, not the technology. Here's what actually goes wrong, and what to look for when choosing an installer.
The real issue
Heat pump technology is proven. It's the same thermodynamic principle as your fridge, running in reverse. Millions of units operate across Scandinavia, Japan, and the rest of Europe. The technology works.
When a heat pump underperforms in the UK, it's almost always because of the installation. Wrong flow temperatures. No heat loss calculation. Weather compensation not configured. Radiators not checked. These are installer errors, not equipment failures.
The five problems below cover the vast majority of heat pump complaints. Every single one is avoidable with a competent installer.
The 5 most common problems
Flow temperatures set too high
A gas boiler runs at 55-65 degrees C. A heat pump should run at 35-45 degrees C. If the installer sets the flow temperature too high, the heat pump works harder, uses more electricity, and costs more to run. This is the single most common cause of high running costs. A properly set up system runs at the lowest effective flow temperature, which is where heat pumps are most efficient.
No heat loss calculation done
Every property loses heat at a different rate. The only way to size a heat pump correctly is to calculate how much heat your home actually needs, room by room. If the installer skips this step and guesses, you end up with a system that's too big or too small. Too big wastes electricity. Too small can't keep up on cold days. A proper heat loss calculation takes a few hours. There is no shortcut.
Weather compensation not set up
Weather compensation adjusts the flow temperature based on the outside temperature. When it's mild, the system runs cooler and uses less electricity. When it's cold, it runs warmer. Without this, the heat pump runs at a fixed temperature all year round, which wastes energy in milder weather and reduces efficiency by 15-25%.
Radiators not checked
Heat pumps run at lower flow temperatures than boilers. Most radiators cope fine, but some older or undersized radiators may not deliver enough heat at 40 degrees C. If the installer doesn't check each radiator's heat output against what the room needs, you can end up with cold spots. The fix is straightforward: upsize the radiators that need it. But it has to be done before installation, not after.
Poor commissioning
Commissioning is the process of testing and optimising the system after installation. Flow rates, pressure, defrost cycles, hot water scheduling, and zone controls all need to be set correctly. If the installer fits the unit and leaves without commissioning properly, the system runs sub-optimally from day one. Good commissioning takes time. It's not something you rush on the last day of a job.
What about noise?
Modern air source heat pumps run at 40-45dB. For context, that's about the same as a fridge, or a quiet conversation across a table. You can stand next to one and talk normally.
Planning rules in England require units to produce no more than 42dB at the nearest property boundary. We position every unit carefully, following MCS guidelines and permitted development rules, to minimise any impact on neighbours.
The noise complaints you read about online typically come from older units (pre-2018 models were louder), units placed directly below bedroom windows, or units installed without proper anti-vibration mounts. All avoidable.
How to choose a good installer
The installer matters more than the brand. A good installer with an average heat pump will outperform a bad installer with a premium one. Here's what to look for.
- MCS accredited. This is non-negotiable. Without MCS, you can't access the £7,500 BUS grant, and you have no consumer protection if things go wrong.
- Does a proper heat loss calculation. If an installer quotes you without visiting the property and measuring every room, walk away. A phone quote is a guess.
- Sets up weather compensation. Ask them directly. If they don't mention it, or don't know what it is, find someone else.
- Uses their own engineers. Companies that subcontract installations have less control over quality. Ask who actually does the work.
- Can show you references. A good installer will have customers who are happy to talk. Ask for references in your area.
- Checks every radiator. During the survey, they should be assessing your radiators against the heat loss figures, room by room. If they don't, they're guessing.
Want it done properly?
We do a full heat loss calculation, check every radiator, and set up weather compensation on every install. No shortcuts.
Common questions
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