The short answer
The physical installation of an air source heat pump typically takes a few days on site for a standard home — commonly around two to five days, depending on how much radiator and pipework upgrading is needed. The outdoor unit, hot water cylinder, controls and commissioning can often be done in this window, with extra time where many radiators need replacing or pipework re-routing. But the full timeline is longer than the days the fitters are present. It also includes the initial MCS heat loss survey and system design, ordering equipment, any required insulation work, and the grant paperwork. From first enquiry to a commissioned system, the end-to-end process often spans several weeks, driven mostly by survey, design and scheduling rather than the install itself. A more complex property, or one needing significant insulation or radiator work first, sits at the longer end.
People usually ask about the days the installers are in the house, but the honest answer covers two timescales: the on-site work and the wider process around it. Both are worth understanding.
Installation timing
- On-site work (typical)Around 2 to 5 days
- Drives on-site lengthRadiator and pipework changes
- Before installSurvey, design, ordering
- End-to-end (typical)Several weeks
- Longer ifMajor insulation or radiator work
Two timescales, not one
When people ask how long a heat pump installation takes, they usually mean one of two different things, and it helps to separate them:
- The on-site work — the number of days the installers are physically in your home fitting the system. This is the disruptive part, when heating and hot water are interrupted while the changeover happens.
- The end-to-end process — the elapsed time from your first enquiry to a fully commissioned, grant-claimed system. This includes everything that happens before and after the fitters arrive.
The honest answer covers both, because they are very different durations. The fitting itself is short, typically a matter of days. The wider journey is longer, usually several weeks, because a heat pump is design-led: a heat loss survey and system design come first, equipment must be ordered, any insulation prerequisites may need addressing, and grant paperwork has to be arranged. Mixing up the two leads to misunderstandings — a household expecting the whole thing to be done in a couple of days can be surprised by the lead time, while one bracing for weeks of disruption is relieved to learn the heating is only off for part of a few days. Knowing which timescale you are asking about is the key to a realistic expectation.
The on-site days: what happens and how long
For a standard home, the hands-on installation commonly takes two to five days. Within that window the team typically:
- Fits and connects the outdoor unit.
- Installs or connects the hot water cylinder.
- Upgrades any radiators identified in the design.
- Runs and insulates pipework and wires the controls and electrical supply.
- Removes the old boiler where it is being fully replaced.
- Commissions the system — filling, pressurising, setting the weather compensation and balancing the heating.
The work usually proceeds in a logical order. Early on, the team prepares the base or wall bracket for the outdoor unit and runs the refrigerant and water pipework between the outdoor unit and the indoor equipment. Mid-job, the cylinder is positioned and plumbed in, any radiators on the upgrade list are swapped, and the electrical connections are made — a heat pump needs its own properly rated supply, which may involve the consumer unit. The final day is typically given over to filling and pressurising the system, wiring and configuring the controls, and the all-important commissioning.
A simple swap with few radiator changes can be at the shorter end; a job with many radiators to replace or awkward pipe routes runs longer. Older properties sometimes spring surprises once floorboards come up or pipe routes are opened, which is why a careful survey beforehand reduces the chance of overruns. Commissioning should never be rushed, as it tunes the system to the low flow temperature it was designed for — getting the weather compensation curve and flow settings right at this stage is what determines whether the system runs efficiently for years afterwards.
The wider timeline from enquiry to working system
The fitters' days are only part of the story. The end-to-end process usually spans several weeks and includes:
- Survey and design: the MCS heat loss survey and system design come first, and good installers may have a waiting list.
- Equipment ordering: the pump, cylinder and any radiators need to be ordered and delivered.
- Preparatory work: if your EPC requires loft or cavity wall insulation for grant eligibility, that may need doing first.
- Grant paperwork: the installer applies for the Boiler Upgrade Scheme voucher.
- Scheduling: fitting the actual install into the installer's calendar.
Each of these stages adds elapsed time even though none of them disrupts your heating. The survey itself takes a few hours, but turning it into a documented design and a fixed quotation can take days or weeks depending on how busy the installer is. Equipment lead times vary with demand and model availability, and a particular cylinder size or radiator type may have to be ordered in. Where insulation work is needed first — to bring a room's heat demand down or to satisfy grant conditions — that is effectively a separate small project with its own scheduling. The grant administration runs in the background: the installer registers the job and claims the voucher on your behalf, with the grant value deducted from your bill rather than paid to you.
So while the heating is only disrupted for the on-site days, the journey from first enquiry to a commissioned, grant-claimed system commonly takes a number of weeks. None of that elapsed time is wasted — it is the design-led nature of heat pumps that makes them reliable once running — but it does mean the process rewards planning ahead rather than leaving it until a boiler fails.
| Phase | Typical duration |
|---|---|
| Survey and design | Allow time to schedule |
| Ordering equipment | Days to weeks |
| Any insulation prep | Varies |
| On-site installation | Around 2 to 5 days |
| Commissioning | Part of on-site days |
Illustrative phases — actual timings vary by installer and property. Sources: Energy Saving Trust; MCS.
Frequently asked questions
How many days will the installers be in my house?
For a standard home, usually around two to five days. The exact number depends on how much radiator and pipework upgrading the design calls for. A straightforward installation with few radiator changes is quicker, while a job needing many new radiators or awkward pipe routing takes longer.
Will I be without heating and hot water during installation?
For parts of the install, yes — while the old system is removed and the new one connected. Installers usually work to restore heat and hot water as quickly as possible. If installation falls in cold weather or someone in the home is vulnerable, discuss timing and any temporary arrangements with your installer in advance.
Why does the whole process take weeks if the install is only a few days?
Because the on-site days are surrounded by survey, design, equipment ordering, any required insulation work, grant paperwork and scheduling. The heat loss survey and system design come first, and good installers may have a waiting list. The fitting itself is short; the preparation and administration around it account for most of the elapsed time.
Sources & further reading
Figures on this page are typical UK ranges drawn from published sources and depend on your specific home. They are guidance, not a quotation or guaranteed saving.