Do I need to be home during the installation?

You don't need to be there the entire time, but you should be available at the start of each day and for the commissioning handover at the end. The installer will need access to your home throughout, and there will be periods without heating or hot water. Most people take the first day off work and arrange for someone to be in on subsequent days.

Will I lose heating during the installation?

Yes, for part of the process. When the old boiler is disconnected and the new system is being connected, you'll have no heating or hot water. This typically lasts a few hours to a full day depending on complexity. If you're installing in winter, ask your installer about temporary electric heaters for that period.

Can I keep my existing radiators?

Often yes. Your installer should do a room-by-room heat loss calculation and check whether each radiator is large enough to heat its room at the lower flow temperatures a heat pump uses. Some radiators may need upsizing, particularly in larger rooms or older properties. Underfloor heating works brilliantly with heat pumps and doesn't need replacing.

How do I check if my installer is MCS certified?

Search the MCS installer register at mcscertified.com. Enter your postcode and it shows every certified company in your area, along with which technologies they're certified for. MCS certification is required for the BUS grant and for Building Regulations compliance. If a company claims to be certified but doesn't appear on the register, don't use them.

What happens if something goes wrong after installation?

Your first call should be to the installer, not the manufacturer. Most installation warranties cover both parts and labour for the first two to five years. The MCS standards require installers to have a complaints procedure and carry insurance. If the installer has gone out of business, the manufacturer's warranty still covers the unit itself. Keep your MCS certificate safe because you'll need it for any warranty claim.

Heat Pump Installation UK 2026: Process, Costs and What to Expect

Two days. That's how long the actual installation took for most of the air source systems fitted under the BUS grant in 2025, according to MCS installer data. But the full journey from "I want a heat pump" to "my house is warm" is longer than that. Four to eight weeks is typical once you factor in the survey, grant application, and scheduling.

This guide walks through every stage so you know exactly what's happening and when. More importantly, it covers what can go wrong and how to spot a bad installation before you're stuck with one.

How Long Does the Whole Process Take?

Here's a realistic timeline:

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Stage	Duration
Getting quotes (3 installers)	1 to 3 weeks
Choosing an installer	A few days
Detailed survey and system design	1 to 2 hours on site
BUS grant application	1 to 3 weeks for Ofgem approval
Waiting for installation slot	1 to 4 weeks
Installation	2 to 5 days
Commissioning and handover	Half a day

Total: four to eight weeks from first quote to heating on. Some of that runs in parallel. Your installer can submit the BUS grant application while you're waiting for the installation slot.

The Survey

This is the most important step, and the one most likely to be rushed by a bad installer.

A proper heat pump survey takes 60 to 90 minutes on site. The engineer should do a room-by-room heat loss calculation, not a quick eyeball. They measure every room, check wall construction, note window types, assess insulation levels, and calculate exactly how much heat your home loses on the coldest day of the year. That number determines the size of heat pump you need.

Here's what your surveyor should check:

Every room measured. Floor area, ceiling height, wall type (cavity, solid, insulated or not), window area and glazing type. If they don't measure, they're guessing.
Existing radiators. Size, type, and location. Heat pumps run at lower flow temperatures than boilers, so some radiators may need upsizing. The survey should identify which ones.
Hot water demand. How many bathrooms, how many people, do you use a lot of hot water? This determines the cylinder size.
Outdoor unit location. Needs good airflow, minimum clearance from boundaries (usually 300mm from walls), and ideally not directly under a bedroom window. Noise at the boundary must stay below 42 dB(A) under permitted development rules.
Electrical supply. Most heat pumps need a dedicated circuit. If your consumer unit is full or your main fuse is only 60A, electrical work may be needed.
Pipework route. How the refrigerant or water pipes get from the outdoor unit to your heating system. Shorter runs are more efficient.

The survey should produce a written report with the heat loss calculation, proposed system size, any radiator changes, and a fixed-price quote. If an installer quotes you over the phone without visiting, find someone else.

Installation Day (and the Days After)

What actually happens when the engineers turn up?

Day 1 is usually the heaviest. The outdoor unit arrives on a pallet. The team installs the concrete base or wall brackets, positions the unit, and runs the pipework through the external wall into your home. If you're having a new hot water cylinder (most installations include one), the old one comes out and the new one goes in. Expect noise, drilling through walls, and some disruption.

You'll lose heating and hot water for part of day 1. A good installer warns you about this and tries to schedule around it. If it's mid-winter, ask about temporary heating arrangements.

Day 2 covers the internal connections. The heat pump gets wired into your electrical supply, connected to your heating circuit, and linked to the hot water cylinder. If radiators need swapping, that happens now. The system gets filled, pressurised, and leak-tested.

Day 3 onwards (if needed) covers any additional work: extra radiators, underfloor heating connections, smart thermostat installation, or tidying up pipework. A simple swap in a modern house might wrap up in two days. An older property with radiator upgrades and complex pipework could take four or five.

Throughout all of this, the installers should protect your floors, clean up daily, and keep you informed about what's happening. If they don't, that's a red flag for the quality of the technical work too.

Commissioning and Handover

This is where a good installer earns their money and a bad one reveals themselves.

Commissioning means setting up the system properly: programming the flow temperatures, configuring the weather compensation curve (which adjusts output based on outside temperature), setting hot water schedules, and running the system through its full operating range to check everything works.

Your installer should spend at least an hour walking you through the controls. You need to understand how to adjust the heating, set timers, and know what the various indicators mean. A heat pump doesn't behave like a gas boiler. You don't crank it up when you're cold and turn it off when you leave. It works best running at a steady, lower temperature for longer periods. If you want to understand the underlying mechanics before your handover, our guide on how heat pumps work covers it in plain terms.

The MCS certificate gets issued after commissioning. You need this certificate for your BUS grant payment and for any future warranty claims. Make sure you receive it. The installer also registers the system with MCS, which is required for the Boiler Upgrade Scheme.

What Can Go Wrong

Here's what most guides won't tell you. These are the problems we see reported most often, and the warning signs to watch for.

Undersized Systems

The single most common problem. An installer picks a unit that's too small for the home's heat demand, either to keep the quote competitive or because they skipped the proper heat loss calculation. The system runs flat out on cold days, can't maintain temperature, and electricity bills are higher than projected.

How to spot it: if the installer hasn't done a room-by-room heat loss calculation, or if their proposed system size is significantly smaller than other quotes, ask questions. A 4-bed detached house rarely needs less than 10 kW. A 3-bed semi typically needs 6 to 10 kW.

Poor Flow Temperature Settings

Heat pumps are most efficient at low flow temperatures, around 35°C to 45°C. Some installers set the flow temperature to 55°C or higher "so the radiators feel hot," which destroys the efficiency advantage. Your COP drops from 3.5 to 2.0 and your running costs double.

How to spot it: after commissioning, check your flow temperature setting. If it's above 45°C and you don't have a specific reason (like very small radiators that can't be replaced), question it.

No Weather Compensation

Weather compensation adjusts the flow temperature based on the outside air temperature. Warmer outside means lower flow temperature, which means higher efficiency. Every modern heat pump supports it. Not every installer sets it up.

How to spot it: ask during the handover. "Is weather compensation enabled?" If they look blank, that's a problem.

Skipping the Cylinder

Some installers try to run a heat pump with the existing hot water cylinder or, worse, with a combi-style setup. Heat pumps need a properly sized, well-insulated cylinder designed for low-temperature operation. A 30-year-old copper cylinder with no insulation will waste energy and leave you with lukewarm showers.

How to spot it: if the quote doesn't include a new cylinder and your current one is more than 10 years old, ask why.

Noise Complaints

The outdoor unit produces 40 to 55 dB(A) at one metre. That's fine in most positions. But placed in a corner where sound bounces off two walls, or directly under a bedroom window, it becomes a problem. Permitted development rules require 42 dB(A) at the nearest neighbour boundary.

How to spot it: the survey should include a proposed unit location with noise assessment. If it doesn't, raise it. Moving the unit after installation is expensive.

Finding an MCS Installer

MCS certification is non-negotiable. You need it for the BUS grant, for Building Regulations sign-off, and for warranty cover. The MCS installer register lists every certified company by postcode.

Get three quotes. Not two, not one. Three. Compare the heat loss calculations, proposed system sizes, and what's included. The cheapest quote isn't always the best, especially if it skips the cylinder or proposes a smaller unit. Before committing, it's also worth reading up on whether a heat pump is worth it for your specific situation.

Ask each installer:

"Can I see the room-by-room heat loss calculation?" (If they can't produce one, walk away.)
"Which brand do you recommend for my property, and why?"
"What flow temperature will the system run at?"
"Will you set up weather compensation?"
"What's included in the warranty, and who do I call if something goes wrong in year three?"

The answers tell you more about the quality of the installation than the brand on the box.

Costs

For a full breakdown of what you'll pay, including the BUS grant, see our dedicated guide to heat pump costs. The short version: air source installations run £10,000 to £16,000 before the £7,500 grant, leaving a net cost of £4,000 to £8,500 for most homes. Ground source costs significantly more. If you're also weighing up solar panels as part of a wider home energy upgrade, our solar panels vs heat pumps guide can help you decide which to prioritise.

Open the eligibility checker. Two minutes. You'll see exactly which grants your home qualifies for and what the net cost looks like.

Common questions

Frequently asked questions

Do I need to be home during the installation?: You don't need to be there the entire time, but you should be available at the start of each day and for the commissioning handover at the end. The installer will need access to your home throughout, and there will be periods without heating or hot water. Most people take the first day off work and arrange for someone to be in on subsequent days.
Will I lose heating during the installation?: Yes, for part of the process. When the old boiler is disconnected and the new system is being connected, you'll have no heating or hot water. This typically lasts a few hours to a full day depending on complexity. If you're installing in winter, ask your installer about temporary electric heaters for that period.
Can I keep my existing radiators?: Often yes. Your installer should do a room-by-room heat loss calculation and check whether each radiator is large enough to heat its room at the lower flow temperatures a heat pump uses. Some radiators may need upsizing, particularly in larger rooms or older properties. Underfloor heating works brilliantly with heat pumps and doesn't need replacing.
How do I check if my installer is MCS certified?: Search the MCS installer register at mcscertified.com. Enter your postcode and it shows every certified company in your area, along with which technologies they're certified for. MCS certification is required for the BUS grant and for Building Regulations compliance. If a company claims to be certified but doesn't appear on the register, don't use them.
What happens if something goes wrong after installation?: Your first call should be to the installer, not the manufacturer. Most installation warranties cover both parts and labour for the first two to five years. The MCS standards require installers to have a complaints procedure and carry insurance. If the installer has gone out of business, the manufacturer's warranty still covers the unit itself. Keep your MCS certificate safe because you'll need it for any warranty claim.