How loud a heat pump actually is
A modern air source unit at a few metres sits in the territory of a dishwasher: a low, steady hum rather than an engine note, loudest when working hard on cold days. It is a sound you notice standing next to the unit and generally stop noticing from inside the house, which is why placement, not silencing, is where the effort goes.
The formal backstop is a noise standard installers must meet for a permitted development installation, assessed at the nearest neighbour's window using the manufacturer's sound data and the geometry of your plot: distance, walls and fences all count. Meeting it is the installer's job, and the calculation belongs in your paperwork, not on your to-do list.
The planning rules, after the 2025 relaxation
For most houses in England an air source heat pump is permitted development: no planning application. The rules were relaxed in May 2025, removing the old requirement to keep the unit at least a metre from the boundary and raising the size limit, so units can now go in the side passages and tight plots that the old rule blocked, provided the noise standard is still met.
The exceptions follow the usual pattern. Listed buildings need consent, conservation areas restrict where the unit can face, flats do not carry householder permitted development rights, and Wales, Scotland and Northern Ireland have their own versions of the rules, so the boundary distance still matters outside England. An MCS-certified installer confirms which regime applies as part of the design.
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Compare heat pump quotesDesigning the problem away
In practice the noise question is solved on the survey. The unit needs clear airflow and a condensate route, and within those constraints a good installer places it away from bedroom windows, yours and next door's, uses the quiet operating modes modern controls offer overnight, and keeps pipe runs short. A few metres of thoughtful placement does more than any acoustic gadget.
If you are weighing a heat pump and the neighbour question has been the sticking point, it is a design detail rather than a dealbreaker in almost every plot. Compare quotes from MCS-certified installers, ask each where they would site the unit and what the predicted level at the nearest window is, and you will hear the difference between a firm that designs and a firm that drops units where the van parks.
Compare heat pump quotes
Up to three trusted, MCS-certified installers quote for the work, grant applied where you qualify. Free, no obligation.
Compare heat pump quotes