Will a heat pump suit your home?

Most UK homes can take a heat pump. The ones that can't are usually obvious: no outdoor space, listed status with no rear access, that kind of thing. The interesting case is the bigger middle, where a heat pump would technically work but the running cost or the up-front cost makes it the wrong call today. Six things decide which side of that line your home sits on.

1. 01 Outdoor space
2. 02 Insulation, walls and loft
3. 03 Radiators
4. 04 Hot water and the boiler
5. 05 Listed and conservation
6. 06 Property type and age

Each is a spectrum, not a yes or no, and where your home sits on each spectrum is what produces a verdict.

If you'd rather skip the explainer, the postcode check uses your home's official EPC record and the same six factors to produce a verdict in about two minutes.

An air-source heat pump needs an external unit. The unit is about the size of a washing machine, typically a metre tall, eighty centimetres wide and forty centimetres deep, and it wants about a metre of clear wall in front of it so the fan can pull air through without recirculating its own exhaust.

Most UK homes have somewhere that works. A back garden is the easy case: the unit sits against the rear wall, plumbing drops back into the property at the boiler position, and the neighbours barely notice. A side return or alleyway can work if it's wide enough that the unit isn't near a facing wall. A roof terrace can work if the building's structure can take the weight, which most can. The case that doesn't work on its own is no outdoor space at all. A first-floor flat with no balcony has nowhere to put the unit, short of an agreement to share an external position with the rest of the building.

Noise is the other thing people ask about. A modern heat pump runs at roughly forty to fifty decibels measured a metre away. That's quieter than a fridge, and well below the legal limit for domestic plant. Permitted-development rules across the UK set a maximum sound power and a minimum distance to the nearest neighbour's window. The MCS installer is responsible for checking your home meets both, and most installs do.

One case worth flagging: terraced houses with side returns. The unit usually fits, but planning rules treat side-of-house installation more strictly than rear-of-house. Sometimes a formal noise assessment is required even when the same install on a rear garden wouldn't need one. Plan for an extra step rather than expecting a refusal.

Insulation matters because a heat pump delivers heat differently from a gas boiler. A boiler runs hot in short bursts; a heat pump runs warm and steady. If the home loses heat as fast as the heat pump puts it in, the system has to push the flow temperature up to keep up, and the running cost goes with it. Better insulation lets the heat pump run cooler, which is what makes it cheap to run.

Before any installer surveys the house, your current boiler will already have told you a lot. Turn its flow temperature down to 55°C and live with it for a few cold days. If the rooms still hold around 19 to 20°C, the fabric is in workable shape and a heat pump will do fine at the same temperature. If the house drifts towards 16°C, or you have to push the boiler back up to 65 or 70°C to keep it warm, heat is leaving the house faster than a heat-pump-temperature flow would replace it, and the answer is to look at insulation first. Running hours tell you something similar. Four hours of heating on a cold day is a comfortable signal. Most of the day on, every day, usually means the fabric is the constraint, not the heat source.

Two insulation jobs change the picture: the loft and the walls. The loft is the easy one. The current target is a 270 mm layer of mineral wool between and over the joists. If you have less than 100 mm or none at all, topping up is one of the cheapest energy retrofits a UK home can do, and ECO4 or the local Warm Homes scheme funds it for a lot of households. If you don't have it yet, it's worth doing whether or not a heat pump is in your future.

The walls are harder, and the answer splits cleanly by construction type. Most UK homes built after about 1930 have cavity walls, and a cavity can be filled with mineral wool or foam from outside in a half-day job. The work is often grant-funded and pays back quickly. If your home has unfilled cavities, fill them first; the heat pump after that costs less to run. The 1930s housing cohort is the canonical case for this, and the 1930s house guide walks through the cavity-versus-solid 9-inch question for that specific era. Solid walls are a different problem. Older terraces, Victorian semis and some rural stone-built homes typically have them. The Victorian house guide walks through the solid-wall question with the realised-SCOP picture and what conservation areas restrict. Solid-wall insulation works, but it's expensive and planning-sensitive, and the running-cost saving from a heat pump alone rarely pays it back. Most solid-wall homes that install a heat pump do so without solid-wall insulation. The verdict tells you that out loud.

The Energy Performance Certificate is the shorthand for the rest of it. Every UK home that's been sold or rented recently has an EPC on a public government register, with a band from A (best) to G (worst). Most homes that take a heat pump without further fabric work sit at band C or D. Band E is the borderline case, where a couple of cheap fabric upgrades (usually a loft top-up plus a cavity fill) often shift the verdict. Band F or G usually means there's a fabric problem worth fixing for its own sake, before anything else.

You don't need to look any of this up yourself. HeatPass pulls your EPC record automatically and combines the band with the things an EPC doesn't cover (radiators, hot water, outdoor space) to produce the verdict.

A radiator's heat output isn't a fixed number. It depends on the temperature difference between the water inside the radiator and the air in the room. Gas boilers send water round at sixty-five to seventy-five degrees Celsius. Heat pumps don't; forty-five to fifty-five is more typical. The same radiator at heat-pump temperatures gives off roughly half the heat it gives off at gas-boiler temperatures.

The formula behind that comes from BS EN 442, the standard every panel radiator sold in the UK is tested against. The output rises with the temperature difference to the power of about 1.3. A radiator rated at a fifty-degree difference (the lab condition) puts out roughly forty per cent of that figure at a heat-pump flow, against eighty-seven per cent at a gas-boiler flow. The curve:

Q = Q₅₀ × (ΔT / 50)ⁿ

Room temp

20°C

Flow–return drop

10°C

Exponent n

1.3 — BS EN 442 panel radiator

The same physics works in reverse on the heat pump side. A heat pump running at a lower flow temperature does more work per unit of electricity it draws. The Coefficient of Performance (COP) at a 50°C flow is typically around 4; at 70°C it drops closer to 2.5. Across a UK winter the seasonal average (SCOP) of a well-designed system lands at 3 to 3.5. That's why a good MCS install would rather oversize a radiator than run the system hotter. The bill-side consequences of where SCOP actually lands are in the running-costs guide.

That doesn't mean every radiator in your home needs replacing. Most UK homes were originally sized with some headroom (and most gas-boiler systems actually run nearer sixty than seventy-five), so plenty of radiators end up about right on a heat pump with no change. But there's almost always a room or two where the original radiator was undersized from the start and only just kept up on gas. The fix is usually swapping that radiator for a larger one, adding a second, or putting in underfloor heating. The MCS installer's quote starts with a room-by-room heat-loss calculation that catches this, and any radiator swaps land in the install quote rather than as a surprise later.

A few practical numbers if you're sizing things up before a quote. Double-panel radiators with two rows of fins put out roughly twice the heat of single-panel ones at the same length. A 1,800 by 600 mm double radiator delivers somewhere between 1.4 and 1.7 kW at a fifty-degree heat-pump flow, depending on the make. Underfloor heating runs cooler still, around thirty-five to forty-five degrees, and pairs well with a heat pump. Retrofitting underfloor heating in an existing UK home is rarely worth the disruption unless you're doing a bigger renovation anyway.

The same survey looks at pipework. Most UK homes use 22 mm or 15 mm copper for the main runs and 10 mm microbore to bedrooms and ensuites. A 10 mm pipe carries about one kilowatt of heat at heat-pump flow temperatures, so the question on each microbore run is whether the room behind it needs more than that. Most bedrooms don't, so the existing pipe stays. The ones that do go on the list to upsize. Pre-1990s homes occasionally used 8 mm gauge throughout, which is rarely enough on its own. A full-house re-pipe lands at about £2,000 in that case, but most homes need only a run or two redone.

Heat pumps need a hot water cylinder. A cylinder is a tank of water, typically 180 to 250 litres for a UK family home. The heat pump warms it over a couple of hours and then holds it at temperature for use through the day. Gas boilers come in two kinds: combi boilers heat water on demand and have no cylinder; system or regular boilers already have one. If you have a combi, the heat pump install adds a cylinder. If you already have one, the install usually replaces it with a slightly larger heat-pump-compatible cylinder.

Modern air-source heat pumps reach the 55 to 60°C the cylinder needs without help from the immersion. The weekly Legionella cycle, set by Building Regs at 60°C, usually runs from the immersion for a few minutes once a week, because a short burst at full electrical efficiency costs less than pushing the heat pump to the top of its range. The cylinder doesn't sit at 60°C the rest of the time. A normal day-to-day setpoint is 48 to 50°C, which is enough for a UK family-sized household and keeps the heat pump on its efficient end of the curve.

Not sure which you have? A small wall-mounted boiler with no separate tank usually means a combi. A few seconds' wait at the tap, with a tank somewhere in the house (often an airing cupboard, sometimes the loft or a utility-room corner), usually means a cylinder.

Adding a cylinder takes space, usually a tall cupboard, a chunk of loft, or a corner of a utility room. In most homes this is a planning question rather than a deal-breaker. Combi homes are the case where the install costs noticeably more than for a home with an existing cylinder, and the HeatPass check surfaces that figure in the cost output rather than burying it.

The fuel you're replacing matters for the financial case more than the technical fit. The install itself is the same regardless of what you're replacing; the savings against your current bill are not. A rough running order, from smallest saving to largest:

• Mains gas is the hardest. Gas is the cheapest mainstream UK heating fuel, so the price gap to electricity is small, and the £7,500 BUS grant is what makes the maths work for most gas-heated homes. Without it, the payback period stretches.
• Oil is a clearer win. It's more expensive than gas per kWh and volatile in price, and a heat pump on a competitive electricity tariff usually pays back inside the system's lifetime even before the grant is counted.
• LPG sits close to oil. Strong financial case, high motivation to switch.
• Direct electric heating (storage heaters, panel heaters, electric boilers) is the strongest case of the lot. A heat pump uses roughly a quarter the electricity to deliver the same heat, so the running cost falls by something close to a factor of three even before tariff optimisation.

None of this changes whether your home is technically suitable, only how soon a heat pump pays for itself once it's in. What each fuel actually costs to run, side by side at 2026 prices, is in the running-costs guide. The HeatPass verdict covers both the suitability and the financial case for your specific home.

Listed buildings can have heat pumps. The cohort is small (listed homes are roughly two per cent of UK housing stock), but the question comes up often because owners assume the answer is no. It isn't. The two extra steps are listed-building consent from the local authority, and an MCS installer with heritage experience.

Listed-building consent is a planning application that weighs how the install affects the property's historic interest. Outdoor units are rarely permitted on the front; the usual position is a rear garden, a side return, or an outbuilding. Internal pipework can be the harder side of the application than the external unit, since running new pipes through a Grade II interior typically needs careful chase work and consent for any visible change.

Conservation areas (homes in a designated zone but not themselves listed) face lighter constraints than listed homes, but still real ones. Permitted development rules are tighter than outside the zone, and the local authority often has an Article 4 direction in force that pulls in a planning application for work that would be permitted in the next street over. For these homes, plan for the extra two months and the application usually goes through. The Victorian house guide covers the conservation-area rules in more depth, since most of the cohort sits in one.

The right MCS installer for a heritage property is a small subset of the wider MCS network. We route these homes only to installers with heritage experience and a track record of successful consent applications. If you're not on a HeatPass check yet, Historic England's energy efficiency guidance is a useful starting point.

Property type and age are useful shorthand, but the five factors above are what actually decide it. A 1930s semi and a 1990s semi share a property type and very little else, and the verdict tracks the fabric, not the label. A few patterns still come up often enough to be worth naming.

Detached and semi-detached houses are the cohort the install was originally designed around. Outdoor space is usually there, the radiators were originally sized for a worse-insulated version of the home, and the cylinder fits in an airing cupboard. The financial case is rarely the reason these homes don't go ahead.

Terraces work, with the side-return wrinkle covered above. Mid-terraces lose less heat than end terraces because two of the four walls are warmed by neighbours, and they often size out to a smaller, cheaper heat pump than the equivalent semi.

Bungalows are the easy case. Single-storey heat-loss is straightforward to calculate, the radiators are usually undersized for any system (because every room has external walls on all sides), and the loft is accessible for top-up insulation in an afternoon.

Flats split. Ground-floor flats with garden access behave like terraces. Mid-floor flats without balconies are the hardest case: with nowhere to put the external unit, the answer is no without a shared building agreement, and HeatPass returns Not Yet on those homes. Some mid-floor flats install air-to-air systems instead of air-to-water, which gives up the £7,500 BUS grant (it doesn't apply to air-to-air) but is a much simpler install.

Period properties (pre-1919, often solid-walled, sometimes listed) are the cohort where broad averages are least useful and a per-home survey matters most. Plenty install heat pumps and the install goes well. Others find the fabric work is the prerequisite, and the Improvement Plan names what.

HeatPass produces one of three verdicts at the end of a check.

"Not Yet" exists because most homes that fail today pass in two or three years once the right fabric or hot-water work is done. The Improvement Plan is the path, not a polite refusal. The installer-vetting page explains how MCS routing works on the Full Pass branch. Nobody is sent to an installer for a home that isn't ready, which is the only thing that makes a Full Pass mean anything.

If you want the verdict for your own address, the check is free and takes about two minutes. Enter your postcode and we'll pull your home's EPC record and ask the things it can't answer.