What a heat pump installation actually involves

A typical UK heat pump install takes 2–5 working days on-site, plus 2–6 weeks beforehand for survey, design and grant processing. Here's the sequence, what a good installer does at each stage, and what disruption to expect at home.

Week 0: enquiry & initial conversation

• You contact 2–3 MCS-certified, BUS-registered installers.
• They ask about property type, age, insulation, current heating, and rough number of radiators.
• A good installer doesn't quote at this stage, they ask to survey.

Weeks 1–2: site survey

This is the most important stage. A proper MCS heat-loss survey is 2–4 hours on-site, measuring:

• Each room's floor area, window area, and existing radiator output.
• Wall construction (solid brick, cavity, timber-frame) and insulation state.
• Loft insulation depth and condition.
• Existing pipework (microbore, 22 mm, 28 mm), this affects whether pipework needs upgrading.
• Outdoor unit location options and condensate drain routing.
• Hot water cylinder location.
• Electrical supply: consumer unit capacity and the main fuse rating (often a stumbling block).

Weeks 2–4: design and quote

The installer sends a written design pack including:

• Total heat loss in kW.
• Specified heat pump model and kW output.
• Designed flow temperature.
• Estimated SCOP.
• Radiators to be replaced (room by room).
• Hot water cylinder size and brand.
• Itemised quote with BUS grant deduction clearly shown.

Weeks 4–6: BUS voucher and contract

• The installer applies to Ofgem for a Boiler Upgrade Scheme voucher.
• Voucher issued (typically 1–2 weeks).
• You sign the contract with a small deposit (10–20% is normal).
• Installation date confirmed, typically 4–10 weeks out depending on the installer's diary and equipment lead times.

Day 1 on-site: prep and outdoor unit

• Installers arrive (typically 2 engineers).
• Outdoor unit position confirmed and base prepared (concrete plinth or wall brackets).
• Outdoor unit delivered, lifted into place, levelled.
• Refrigerant pipework routed to the indoor location, drilling 1–2 wall penetrations.
• Condensate drain routed to a downpipe or soakaway.

Day 2: indoor plumbing and cylinder

• Old hot water cylinder removed if applicable. Combi boiler isolated (or removed if you're going full electric).
• New unvented cylinder installed.
• Heat pump heat exchanger and buffer connected.
• Hot water mains pressure tested.
• System filled, vented, flushed.

Day 3: radiator changes and electrical

• Identified radiators replaced (usually 1–3, sometimes none).
• Smart thermostat and weather-compensation sensor installed.
• Electrical works: dedicated heat pump circuit, isolators, possibly a consumer unit upgrade.

Day 4: commissioning and handover

• System started and run through manufacturer commissioning procedure.
• Flow temperature set, weather compensation curve adjusted.
• SCOP verified against design.
• Installer walks you through controls.
• MCS certificate issued.
• Building Control notification submitted (if required).
• Manufacturer warranty registered.

What disruption to expect at home

• No heating for a few hours during cylinder swap on day 2.
• No hot water for half a day on day 2.
• Outdoor noise while drilling and craning the outdoor unit.
• Indoor mess in the rooms with radiator changes, installers should sheet up.
• Electrical disruption for 1–2 hours if the consumer unit is being upgraded.

What "fully commissioned" should mean

By the end of day 4 you should receive:

• MCS certificate (PDF and original on paper).
• Manufacturer commissioning report.
• Heat-loss survey and design pack.
• Warranty registration confirmations.
• Quick-start guide for the controls.
• Annual servicing booking for ~12 months out.

Common things that go wrong (and aren't deal-breakers)

• Refrigerant leak during commissioning. Caught at install. Installer fixes and re-charges.
• Flow temperature too high on day 4. Comes down as the installer dials in weather compensation over the first cold week.
• One room slow to heat. Usually a balancing issue, fixed without parts.
• Cylinder noise. Air in the system; bleeds out over a week.

What a good installer does differently on day 1

The difference between a competent install and a rushed one usually shows up before any pipework is touched. A good engineer walks the access route with you first, protects flooring and carpets with dust sheets, and confirms the exact outdoor unit position against the design pack rather than picking a convenient spot on the day. If the base needs a concrete plinth, that should have been agreed during the survey stage, not improvised on day one. Ask to see the design pack on-site if it isn't already in the installer's hands, it should match what you were quoted.

What happens if something doesn't go to plan

Real installs occasionally hit snags: a wall turns out to be solid where the survey assumed cavity, the electrical supply needs more work than expected, or a delivery is delayed. A competent installer flags this immediately rather than pushing ahead and hoping, and any cost implication should come back to you in writing before extra work proceeds. If a genuinely unexpected issue adds more than 10% to the agreed price, that's worth a conversation before you authorise it, not a surprise on the final invoice.

How installation timelines vary by property type

The 2 to 5 day figure covers a typical semi or terrace with a straightforward outdoor unit location. A few things stretch it: a consumer-unit or main-fuse upgrade from your electricity network operator adds 2 to 4 weeks of separate scheduling (the work itself is quick but the DNO's queue isn't). Ground source installs add 5 to 15 days for trenching or borehole drilling before the indoor work even starts. Listed buildings or conservation areas can add weeks to the planning stage if the outdoor unit needs consent. Ask your installer for a property-specific timeline rather than relying on the generic figure.

Preparing your home before the installers arrive

A few things speed the install and reduce disruption: clear access to the loft if loft insulation needs checking, clear the area around the proposed outdoor unit position, and move anything valuable or fragile out of rooms where radiators are being changed. If you have pets, plan for them to be elsewhere on day one when the outdoor unit is delivered and craned into place, that's the noisiest and busiest part of the process. Keep the design pack and quote to hand so the on-site team can check what was agreed against what they're fitting.

Who's on-site and when

Most installs use a team of 2 engineers for the core install days, sometimes joined by a dedicated electrician for a half or full day if a consumer-unit upgrade is needed. Larger ground source installs bring in a separate drilling or trenching subcontractor for the ground array stage, working ahead of the plumbing and electrical team rather than alongside them. Ask your installer who's actually attending each day, and whether that's the same team that did your survey, continuity between survey and install reduces the chance of something being missed or miscommunicated.

Building Control notification is required for most heat pump installs under Part L and Part P of the Building Regulations. A competent MCS-certified installer self-certifies this as part of the standard process, you shouldn't need to contact your local authority separately. Keep the notification confirmation with your other paperwork, you may need it if you extend or sell the property later.

If you're claiming the BUS grant, keep every document the installer gives you, the design pack, the signed contract showing the gross and net price, the MCS certificate, and the commissioning report. These aren't just filing paperwork, they're what you'd need if a dispute arose over workmanship, if you sell the property and a buyer asks for proof of the grant-funded install, or if you ever need to claim on the manufacturer or workmanship warranty.

The first few weeks after commissioning

It takes a heating season, not a few days, to properly judge a heat pump install. Expect some fine-tuning in the first few weeks as the installer (or you, with their guidance) adjusts the weather compensation curve based on how the property actually behaves versus the design assumptions. Don't panic if the first cold snap feels different from a gas boiler, that's expected, heat pumps run more continuously at a lower output rather than cycling hard. If a room genuinely stays cold after a few weeks of settling in, that's when to call the installer back, not before.

Find your installer

Start with our regional directory and use the questions to ask guide.