Air Source Heat Pumps
Air source heat pumps deliver low-carbon heating and hot water that generates more energy than it uses — with £7,500 Boiler Upgrade Scheme grant support.
Done properly, by a local team
Boiler Upgrade Scheme
Grants towards eligible heat pumps are claimed by an MCS-certified installer — we are one, so we handle the application and check what your property qualifies for.
Replacing oil or LPG?
Off-grid homes can get up to £9,000 — see our oil and LPG heat pump guide.
Designed for your home
We size and design the system properly so it's efficient and comfortable.
How an air source heat pump actually works
A heat pump is a refrigeration circuit run in reverse. A fan draws outdoor air across an evaporator holding refrigerant that boils well below zero, so even air at 2°C carries enough energy to turn it to gas. A compressor squeezes that gas, raising its temperature sharply, and a second heat exchanger hands the heat to the water circulating through your radiators and cylinder. Nothing burns, so the output is not capped at the energy you put in. For each unit of electricity the compressor draws, a heat pump moves roughly three units of heat indoors averaged across a year, and closer to four in a well-designed system running at a low flow temperature. Set up badly, it can drop below three. That ratio is the coefficient of performance, and it shifts with the outdoor temperature and with how hot you ask the water to be. The rhythm differs too: a boiler fires hard and stops, while a heat pump runs long and low, matching the heat the house is losing.
Flow temperature is the number that decides your bill
Flow temperature is how hot the water leaving the heat pump is. A gas boiler is often left at 70-75°C; a heat pump is designed around 35-50°C, and that gap matters more than the badge on the unit. That is a regulatory expectation as well as a commercial one: Part L of the Building Regulations requires a new or fully replaced wet heating system in England to be designed for a maximum flow temperature of 55°C where the property allows. The smaller the lift between outdoor air and flow temperature, the less work the compressor does. As a working rule each degree off the flow temperature returns roughly 2-2.5% in efficiency, so designing at 45°C rather than 55°C is worth around a fifth of your heating bill for the same comfort. SCOP, the seasonal coefficient of performance, is the year-round average including cold spells and defrost cycles. Manufacturers quote it at a stated flow temperature, so a figure taken at 35°C says little about a system designed at 55°C. In the government-backed Electrification of Heat trial the median measured performance across air source installations was 2.80; a 2025 study of 169 openly monitored UK systems on HeatpumpMonitor.org — a self-selected, closely tuned sample rather than a representative one — averaged 3.86. Most of that gap is design and controls, not hardware.
The heat loss survey, and why your radiators may change
No one can price a heat pump from a photograph of your boiler. Design begins with a room-by-room heat loss calculation to BS EN 12831-1: external walls, windows, floors and roof measured, U-values assigned by construction and age, ventilation and air changes added, and the total run at the design external temperature MCS assigns to your postcode from CIBSE Guide A Table 2.5, the 99.6th percentile of dry-bulb hours, adjusted for altitude. On Merseyside that lands around -2°C, though the exact figure comes from the nearest reference weather location to your address. That gives a watts figure for every room and a total for the house, and under the MCS design standard the heat pump must cover 100% of it. Every radiator is then checked against its room's figure at the design flow temperature, not at boiler temperature, and this is where retrofits get expensive. Radiator output falls steeply as the water cools: a panel giving 1,000W at 70°C flow may manage little over half of that at 50°C. Some rooms need a deeper K2 or K3 panel in the same wall space, some need nothing, and old 8mm microbore can throttle flow.
Hot water, cylinders and the combi question
A heat pump cannot heat water on demand the way a combi does, so hot water is stored. Around 180-250 litres suits most family homes, and reheat is slower but far quieter. Cylinders built for heat pumps carry a much larger internal coil, because cooler water needs more surface area to move the same heat. Connecting one to an old boiler cylinder is a common cause of poor performance and long reheat times. Stored water usually sits at around 48-52°C, ample through a shower mixer. Building Regulations Part G caps the bath outlet at 48°C on new and replacement installations, so a blending valve is fitted. To control legionella risk the system runs a periodic pasteurisation cycle to 60°C, typically weekly and often with help from the immersion heater. In an owner-occupied home that weekly cycle is the accepted approach; landlords and premises covered by HSE's Approved Code of Practice L8 carry separate duties, so tell us if the property is let. Unvented cylinders are notifiable under Part G and need a proper discharge route.
Noise, siting and permitted development
The outdoor unit sits on ground feet or a wall bracket, with clear air in front of the fan and a condensate route that will not ice a path. Expect roughly 40-50 dB(A) at a metre: the quiet end is fridge-like, the upper end closer to conversation, with a more noticeable note during defrost cycles in damp, cold weather. Watch the units when comparing models — manufacturers often publish sound power (Lw), a larger figure than the sound pressure quoted here. Planning catches people out. In England most installations are permitted development, but the rules were rewritten on 29 May 2025. The one-metre boundary rule has gone, the unit may be up to 1.5 cubic metres at a house, and detached homes may have two. On a flat roof it must sit at least a metre from the edge; pitched roofs are excluded. Two further limits trip people up: a unit used solely for cooling falls outside permitted development altogether, and outside a conservation area a wall-mounted unit cannot go above ground-floor level on an elevation fronting a highway. Since the transitional period closed on 28 May 2026, MCS 020 a) is the only sound calculation accepted for permitted development in England, and it must come out at 37.0 dB LAeq,5min or less one metre from every habitable-room window and door of neighbouring properties. Passing it does not by itself grant permitted development: the rest of the Class G conditions still apply, and conservation areas and listed buildings carry extra restrictions on top.
Running costs against your gas boiler: the arithmetic
Under the Ofgem cap for 1 October to 31 December 2026, electricity averages 26.32p per kWh and gas 7.97p, a ratio of about 3.3 to one. A condensing boiler in a real house rarely reaches its laboratory figure, particularly when it is run at 70°C and barely condensing, so 85% is a fair working assumption. That puts a useful kilowatt-hour of gas heat at roughly 9.4p. A heat pump averaging a seasonal 2.8 costs about 9.4p for the same heat, which is level. At 3.3 it is about 8p. At 3.8 it is about 6.9p. Break-even sits close to 2.8 — the 3.3 price ratio divided by the boiler's 85% efficiency — which is why flow temperature and design carry more weight than the manufacturer you pick. That figure moves with the boiler you assume: about 3.0 against a 90% boiler, about 2.6 against an 80% one. That is before standing charges, before heat pump tariffs, and before the gas standing charge disappears if you remove gas. The calculator on this page runs the same arithmetic on your own consumption and rates. Rates correct as at 9 September 2026, for the Ofgem cap covering 1 October to 31 December 2026; it changes quarterly. One quirk matters: VAT on domestic electricity is suspended from 1 October 2026 to 31 March 2027, so the 26.32p carries no VAT while the 7.97p gas figure does. When it returns on 1 April 2027 the effective electricity rate rises to about 27.6p and break-even moves to roughly 2.9.
The Boiler Upgrade Scheme, described neutrally
The Boiler Upgrade Scheme is a government grant in England and Wales: currently £7,500 towards an air source heat pump, and the 2026 amendment regulations extended it to the financial year beginning 1 April 2029, so it now runs to 2030. Homes with no mains gas connection heated by oil or LPG can claim a further £1,500 until March 2027, taking an air source or ground source grant to £9,000. Air-to-air systems became eligible on 28 April 2026 and attract £2,500, without the £1,500 uplift. Installation is zero-rated for VAT until 31 March 2027, reverting to 5% afterwards. It is installer-led: the grant is claimed through an MCS-certified installer, who applies so the money comes off your quoted price rather than reaching your bank. That certification is a scheme rule, not a preference. Since 28 April 2026 you no longer need a valid EPC to apply: where the property has one it goes in with the application, and where it does not, the installer supplies the alternative evidence the scheme accepts. The requirement to clear outstanding loft and cavity insulation recommendations has gone too. New builds and social housing are excluded, self-builds are eligible, there is one grant per property, the work must finish within 120 days of the application, and hybrids do not qualify. Neutrally put, £7,500 rarely makes a heat pump cheaper than a like-for-like boiler replacement; it narrows the gap.
Simple, from quote to comfort
- 1
Free survey & fixed quote
We visit, assess your home and give a clear fixed price — no pressure, no jargon.
- 2
Pick a date that suits you
Choose a day that works. We confirm everything up front and answer any questions.
- 3
Tidy, Gas Safe install
Our engineers fit your system cleanly and safely — and leave your home spotless.
- 4
Aftercare & guarantee
You're covered by the manufacturer guarantee, with our local team a phone call away.
Related services
What could a heat pump cost you to run?
Put in what you spend on heating now and we'll estimate the running cost of an air source heat pump against it. It uses your real bill rather than a national average — and it shows its working.
What heats the home now?
Your current costs
The heat pump
A lower flow temperature means a more efficient heat pump. We estimate seasonal efficiency (SCOP) from it — currently 3.56.
A 17% lower running cost
Get a proper heat-loss surveyHow was this calculated?
- Fuel energy bought
- 17,143 kWh/yr
- Existing efficiency
- 80%
- Useful heat needed
- 13,714 kWh/yr
- Estimated SCOP
- 3.56
- Heat pump electricity
- 3,852 kWh/yr
- Heat pump running cost
- £1,001.61
This is an indicative comparison based on the figures you enter and the assumptions shown. Real heat pump performance depends on your property's heat loss, system design, radiator sizing, weather, controls, hot water demand and tariff. It is not a substitute for a full heat-loss calculation and system design, which we carry out before quoting.
Common questions
Will a heat pump work in a Victorian terrace or a 1930s semi?
Usually yes, but the survey decides that, not the age of the house. What matters is the heat loss figure and whether your emitters can deliver it at a sensible flow temperature. Solid-wall terraces lose more heat, so they often need a larger unit and several upsized radiators, which pushes the design flow temperature up and the running cost with it. Loft and cavity insulation, where it is possible, lowers both the equipment size and the bill.
Do I have to replace every radiator?
Rarely. The calculation is done room by room, so it is normal for a handful of rooms to need a deeper panel in the same wall space while the rest stay exactly as they are. Bedrooms and hallways often pass; north-facing living rooms and extensions often do not. If someone tells you before surveying that no radiators need changing, or that all of them do, treat both answers with suspicion.
Will my neighbours be able to hear it?
Most modern units run around 40-50 dB(A) at a metre, which is quieter than typical street noise. For permitted development the MCS 020 a) calculation has to show 37.0 dB(A) or less at one metre outside every habitable-room window and door of neighbouring properties, not just the nearest one, so siting is assessed before installation rather than argued about afterwards. Position, distance, screening and nearby reflective surfaces all feed into that figure.
Will it definitely be cheaper to run than my gas boiler?
No, and anyone promising that is guessing. At current cap rates electricity costs roughly 3.3 times as much as gas per unit, but a gas boiler only converts about 85% of that gas into useful heat in a real house. Divide one by the other and a heat pump needs a seasonal efficiency above roughly 2.8 to beat a gas boiler on running cost. That is almost exactly the 2.8 median measured in the government's Electrification of Heat trial, so an average installation lands about level and a well-designed one saves — which is why the design, not the badge, decides your bill. A low flow temperature and correct weather compensation are what lift you clear of it, and systems designed at 55°C routinely fall short. Run your own numbers through the calculator on this page.
I have a combi boiler, so where would the cylinder go?
You need somewhere for 180-250 litres plus access for maintenance. Airing cupboards are the usual home, lofts are workable where the structure and pipe runs allow, and otherwise it means losing a cupboard or boxing in a corner. This is often the deciding factor in a small terrace, so it is worth measuring before you gather quotes. Removing the gas boiler and capping the supply is Gas Safe work; our registration is 541116.
Do I need planning permission?
Most Merseyside installations do not, because they fall under permitted development in England. The exceptions matter though: listed buildings, scheduled monuments, and conservation areas where the unit would face a highway. Flats are limited to one unit of no more than 0.6 cubic metres, and a unit installed solely for cooling falls outside permitted development wherever it sits. If your property sits in one of Liverpool's conservation areas we check before quoting rather than after, and the same check applies across all 209 towns and districts we cover. Call 0151 440 2000 if you want that checked first.
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