Heat pump FAQ

The questions UK homeowners actually ask before going ahead. We've answered each one as briefly and accurately as we can, with no marketing fluff.

Are heat pumps noisy?

A modern ASHP outdoor unit runs at around 40 to 45 dB at 1 metre, quieter than a fridge in a kitchen and well below the 42 dB MCS Permitted Development Rights limit measured at a neighbour's window². Older units (pre-2018) can be noisier. If you're sensitive to sound, ask the installer for the manufacturer's dB(A) rating at 1 m and at 4 m for the specific model.

Do heat pumps work in winter?

Yes. UK ASHPs are rated to operate down to −15°C, well below the coldest temperature most of the UK sees. Output drops as it gets colder, which is why MCS heat-loss surveys design for your local "design day" (the coldest 1% of hours). A properly sized heat pump will heat your home through a UK winter without resorting to immersion heater backup.

Will I need new radiators?

Often one or two, occasionally none, occasionally three or four. Heat pumps run at lower flow temperatures than gas boilers, so radiators need more surface area for the same heat output. The MCS heat-loss survey identifies which rooms need bigger radiators. Allow £200 to £500 per radiator.

Can I keep my existing radiators?

Yes if they're already oversized for your gas boiler's flow temperature (common in 1990s to 2010s installs) or if your installer designs for a higher flow temperature (~55°C) and accepts a lower SCOP. The trade-off is between capital cost (radiator changes) and running cost (lower SCOP).

Do I need underfloor heating?

No. Underfloor heating works very well with heat pumps because it operates at low flow temperatures, but it's not required. Most UK retrofit installs use radiators.

What about hot water?

A heat pump heats a hot water cylinder, typically a 200 to 250 L unvented cylinder. You'll have stored hot water like a system or regular gas boiler property, no combi-style instant hot water. The cylinder is heated to 45 to 48°C and a weekly Legionella cycle takes it to 60°C.

Will it heat my Victorian terrace?

Yes, but the design matters more than for a modern semi. Heat-loss surveys for older properties need to factor in single-glazed sashes, solid walls and chimney draughts. Some properties benefit from insulation upgrades first; others can take a heat pump as-is with bigger radiators. Don't accept a quote that ignores the property's age.

Will it heat my home faster than a gas boiler?

No. A heat pump heats your home gradually and steadily. It's designed to run more or less continuously through cold weather at a low flow temperature, rather than blasting on and off. You'll learn to set targets around an hour earlier than you would with a gas boiler. Many heat pump owners report the house is more consistently warm than under a boiler.

Do I need planning permission?

Usually no. Most ASHP installs in England fall under Permitted Development Rights as long as the outdoor unit is under 0.6 m³, more than 1 m from the property boundary, and meets a 42 dB noise limit at the nearest neighbour's window². Listed buildings, conservation areas and some London boroughs have additional restrictions. Your installer should check and tell you.

Can a heat pump cool my home in summer?

Most modern ASHPs can run in cooling mode, same refrigerant cycle in reverse. UK installs rarely commission cooling because it draws power on summer days, radiators don't distribute cool air well (underfloor heating and fan coils do), and condensation can cause damage to flooring and pipework. If you specifically want cooling, ask your installer to design for it.

Are heat pumps right for flats?

Possible but harder. A balcony or accessible flat roof can host an outdoor unit; some buildings have communal heat pumps serving multiple flats. Freeholder permission is usually required and not always given. Air-to-air heat pumps (heat pump-style aircon units) are sometimes used in flats, but they're not BUS-eligible.

How long do they last?

Manufacturer life expectancy is 15 to 20 years on the heat pump itself, similar or longer for the cylinder. Compressor warranties are typically 5 to 7 years from the manufacturer, with a longer parts warranty.

What if it breaks?

Annual servicing catches most issues before they become breakdowns. For breakdowns, your installer (if MCS-certified and signed up to the MCS workmanship warranty) is the first point of contact. The manufacturer's warranty covers the heat pump itself; the workmanship warranty covers the installer's work for typically 2 to 6 years.

What's the carbon impact?

A UK ASHP at SCOP 3.5 emits roughly 80% less CO₂ than a gas boiler, calculated on the current grid mix³. As the UK grid continues to decarbonise (60% low-carbon in 2026, projected ~85% by 2030), the gap will widen. A heat pump installed in 2026 will emit less every year of its life as the grid cleans up.

Can I install a heat pump myself?

No, not if you want the Boiler Upgrade Scheme grant or a workmanship warranty. BUS explicitly requires an MCS-certified installer to design, install and commission the system. Beyond the grant, heat pump installation involves refrigerant handling (F-Gas regulations require certification), electrical work notifiable under Part P, and heat-loss calculations that materially affect performance if done wrong. This isn't a competent-DIYer weekend project in the way a radiator swap might be.

Does my EPC rating affect eligibility?

For the Boiler Upgrade Scheme, your EPC must not have outstanding recommendations for loft or cavity wall insulation, and it needs to be less than 10 years old at the time you apply. If your EPC has lapsed or flags insulation work, you'll need a new assessment or to complete the recommended work first. See our Boiler Upgrade Scheme guide for the full eligibility rules.

What size heat pump do I need?

There's no shortcut formula that reliably substitutes for a proper MCS heat-loss survey. Rough rules of thumb based on floor area exist, but they ignore insulation quality, glazing, orientation and construction type, all of which materially change the answer. An 8kW to 12kW unit covers most 3 to 4 bedroom UK homes, but the only way to know your actual figure is a room-by-room survey. Undersizing means the system struggles on the coldest days; oversizing wastes money and can hurt efficiency through excessive cycling.

Can I get a heat pump if I rent my home?

Only with the landlord's agreement, since it's a permanent alteration to the property and the freeholder or landlord will need to be the applicant for the Boiler Upgrade Scheme in most cases. If you're a landlord considering one for a rental property, BUS is open to small landlords as well as owner-occupiers, though the property still needs a compliant EPC. Tenants interested in a heat pump should raise it with their landlord directly rather than approaching installers themselves, since the contract and grant application need to be in the property owner's name.

Do heat pumps need a lot of maintenance?

Less than most people expect. Beyond the annual service, day to day maintenance is minimal, keep the outdoor unit's air intake clear of leaves and debris, check the condensate drain isn't blocked, and glance at the system's fault light occasionally. There's no equivalent of a boiler's annual gas safety check requirement, though the annual service serves a similar purpose for catching small issues early.

Can I switch installers partway through?

Legally yes, but practically it's disruptive and can void warranty continuity if the second installer didn't do the original design. If you're unhappy with an installer before work has started, it's far simpler to walk away and get a fresh quote elsewhere than to try switching mid-project. Once installation has begun, raise concerns with the installer directly first, most issues are resolvable without needing to change contractor entirely.

Still have a question?

If you've got a heat pump question we haven't covered, get in touch and we'll consider it for the next update.