Before anything happens: the survey
Someone comes round first — usually for an hour or two. They’ll look at your radiators, your loft insulation, your hot water tank (if you have one), and where the outdoor unit could go.
This isn’t a sales visit dressed up as a survey. A good installer will tell you honestly if your house needs work first. That might mean bigger radiators or more insulation before a heat pump will work well. It’s usually more thorough than a typical boiler quote visit, so don’t be surprised if it takes a while.
Treat it as a two-way conversation, not something that just happens to you. This is where decisions get made about changes to your home, so ask questions — including things you might want, not just things they’re planning. For example, if you’re thinking about moving a radiator, ask about it. Installers can often use heat cameras to trace existing pipes under floors or walls. That tells you how feasible a move is, and roughly what it’d involve.
There’s also a fair bit to sort out on your side before install week — access, deliveries, sign-offs. It’s enough to deserve its own page: Getting your house ready for a heat pump install: a checklist.
The install itself: how long, how messy
For most homes, it takes 2 to 4 days. Here’s roughly what happens:
Day 1 — Old boiler comes out (if you’re replacing one). Outdoor unit position gets marked and pipework starts.
Day 2 — Radiators often get swapped for bigger ones, since heat pumps work best running at lower temperatures for longer. This is the messiest day — expect some dust, and rooms being out of action one at a time.
Day 3 — Hot water cylinder goes in, if you didn’t have one already. Pipework gets connected up.
Day 4 — Everything gets tested, commissioned, and the engineer talks you through the controls.
You’ll have hot water and some heating most of this time, just not always in every room at once.
The noise — what people actually notice
This is the question everyone asks and almost nobody gets a straight answer to.
A modern air source heat pump running normally sounds a bit like a quiet extractor fan, or a fridge humming outdoors. Standing right next to it, you’ll hear it. From inside the house with windows shut, most people don’t.
It’s not silent. If your outdoor unit ends up near a bedroom window or close to a neighbour’s fence, that’s worth thinking about at the survey stage. Better before it’s installed than after.
Cold weather doesn’t stop them working, either — modern heat pumps are built to keep running well below freezing. If that’s the thing making you hesitate, it’s an outdated worry, not a real limitation.
Living with it, week to week
The biggest adjustment isn’t the pump — it’s the habit change:
It runs longer, at a lower temperature. Instead of blasting hot for an hour then switching off, it might run gently for most of the day. Radiators feel warm, not scorching, and that’s normal — it’s working properly.
You mostly stop touching the thermostat. Once it’s set up, turning it up and down like a gas boiler tends to make it less efficient, not more comfortable.
Hot water works differently. Many systems heat water once or twice a day rather than on demand. You get used to it fast, but it’s a change from a combi boiler.
What surprises people, good and bad
Good surprises:
Rooms feel more evenly warm. Not the hot-then-cold swings you get with a boiler.
It’s quieter than people expect. Once you’re not stood right next to the outdoor unit, you barely notice it.
Bills can genuinely drop. Especially alongside better insulation.
Less good surprises:
Bigger radiators change the look of a room. Some people don’t love that trade-off.
It runs more constantly than a boiler. The first few weeks of that can feel odd until you’re used to it.
Skipping insulation shows up fast. If it wasn’t sorted out first, the house can feel harder to keep warm than expected.
When things go wrong (they sometimes do)
Worth knowing about, not to worry you, but so it doesn’t catch you off guard.
If you’re moving from an old non-pressurised system to a pressurised one, turning the water on for the first time can find weak points in old plumbing. Think loose caps or fittings that were fine before, but start leaking under new pressure. This isn’t the new install being faulty; it’s the old system’s weak points getting found. A decent installer tests thoroughly and sorts leaks as part of commissioning, before they leave.
Mistakes can happen too. Install teams sometimes include apprentices learning on the job under a lead installer. Most of the time that’s fine, but occasionally something needs a second look and correcting. Don’t be afraid to ask your installer to double-check everything before they call the job finished.
Who this probably doesn’t suit
Poor insulation, no plan to fix it first. Heat pumps work best once that’s sorted.
Nowhere sensible for an outdoor unit. Very tight spaces, especially away from windows or boundaries, can rule it out.
Expecting a zero-change swap. Radiators or pipework almost always need some work too.
Who this tends to suit well
Already reasonably insulated. Or willing to put the work in to get there.
Happy to leave it running steadily. Rather than switching the heating on and off like a boiler.
Replacing an old, inefficient boiler anyway. That’s often when the numbers make the most sense.
Summary
The short version
The survey sets the tone
A good installer tells you what your home actually needs — not just what you want to hear.
2 to 4 days, some mess
Radiators, cylinder, and pipework get swapped in stages. You’ll have hot water most of the time.
Quieter than you’d think
You’ll hear it standing next to it. From inside with windows shut, most people don’t.
Runs low and steady
The biggest adjustment is habit, not hardware — you mostly stop touching the thermostat.
Old plumbing can surprise you
Pressurising an old system can reveal weak joints that were already there — not a new fault.
Not universal, and that’s fine
Suits homes that are insulated (or willing to be), replacing an old boiler anyway.
Just Ask: Heatpump
Just Ask: Heatpump is an independent companion to Visit a Heat Pump and Get a Heat Pump. Built from real installation experience to give honest, practical guidance before you commit.
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