Heat Pump Radiators In The High Peak, Greater Manchester, Sheffield And Leeds: Do Yours Need Changing?
Some of your radiators will stay and some will grow, because each catalogue output assumes water at 70°C.
Key Takeaways
- A radiator rated at 1,000 W in the catalogue gives about 460 W with heat pump water at 50°C flow, and about 354 W at 45°C (method and table below).
- In a government trial of 742 heat pump installs, 93% had new emitters fitted. A 2025 study of boiler data from about 4,600 homes found 31% could run at 55°C or lower with the radiators they already had, with the heating spread over longer periods.
- Kitchens and bathrooms were the rooms the trial’s designers flagged most for radiator problems, because wall space runs out there first.
- Microbore pipes can work. Long microbore runs are the ones most likely to need replacing.
- Our design names each radiator that stays and each one that grows, before you get a fixed quote.
In This Guide
Look up the radiator in your front room in its maker’s catalogue and the output listed beside it assumes water at around 70°C. A 2025 study of UK homes puts gas boilers at 60 to 70°C and heat pumps at their best below 45°C. Feed the same radiator 45°C or 50°C water and it gives out between a third and a half of its catalogue figure.
That gap sits behind the fear of a heat pump that leaves the house cold. In a gritstone terrace in New Mills, a 1930s semi in Stockport or a Victorian terrace in Leeds, the answer comes from the same sum: the heat each room loses on a cold day, set against what its radiator gives out at the water temperature your heat pump will run.
The Catalogue Figure Assumes Water At 70°C
Radiator makers in the UK test and rate their radiators under the European standard EN 442. The headline figure, called the ΔT50 output, comes from a test where the average temperature of the water inside the radiator sits 50°C above a 20°C room, so the water averages 70°C (Zehnder, Correction Factors (Delta T Conversion), read 13 October 2026).
ΔT is that gap between the average water temperature and the room. Shrink the gap and the output falls faster than the gap does. The makers’ own conversion raises the ratio of the new gap to 50 to the power 1.3, a fit Zehnder states represents the heat output of most radiators. Run your heat pump at a lower temperature and the radiator gives out a smaller share of its catalogue number, as the table shows.
| Water temperature (flow / return) | Average water temperature | ΔT in a 20°C room | Share of catalogue output | A radiator rated 1,000 W gives | Catalogue output needed for the same heat |
|---|---|---|---|---|---|
| Catalogue rating (ΔT50) | 70°C | 50 | 100% | 1,000 W | 1.0 times |
| 55°C / 50°C | 52.5°C | 32.5 | 57% | 571 W | 1.75 times |
| 50°C / 45°C | 47.5°C | 27.5 | 46% | 460 W | 2.2 times |
| 45°C / 40°C | 42.5°C | 22.5 | 35% | 354 W | 2.8 times |
| 40°C / 35°C | 37.5°C | 17.5 | 26% | 255 W | 3.9 times |
Our arithmetic, using the EN 442 rating point and the 1.3 exponent above, with the water cooling by 5°C between flow and return. A room you keep at 21°C does a little worse: at 50°C flow the share drops from 46% to 44%. If a maker publishes its own ΔT30 or lower figures for a model, the design uses those instead.
A worked example
Take a room that loses 1,200 W on a cold design day, heated today by a radiator rated 1,600 W in the catalogue. With a boiler at 70°C that radiator has plenty in hand. At 50°C flow it gives about 740 W, so the room falls short by about 460 W and stays below temperature in a cold snap.
To cover that room at 50°C flow you need about 2,600 W of catalogue output, and about 3,400 W at 45°C flow. These figures illustrate the method and come from no measured house. Your survey replaces them with the heat loss of your own rooms.
Do You Need New Radiators For A Heat Pump? Two Studies, Two Answers
A large government trial points one way. The Electrification of Heat project, funded by the government and delivered by E.ON, OVO and Warmworks, installed 742 heat pumps, and 93% of them went in with new heat emitters because the existing radiators were too small for the output needed (LCP Delta for BEIS, Electrification of Heat Demonstration Project: Home Surveys and Install Report, December 2022). Contractors told the researchers they tended to replace all the radiators in a house once they changed any, though the report could not verify it. The report also found a trend of over-caution in the industry, sizing systems up and adding more radiators than the design required.
A 2025 study read the other way. Researchers from UCL, DESNZ, Loughborough University and the University of Birmingham used diagnostic data from about 4,600 internet-connected combi boilers in England and found 31% of the homes could run at 55°C or lower without any radiator upgrades, with the heating spread over longer periods, against 10% in the earlier government surveys (CIBSE Journal, How ready are UK buildings for heat pumps?, January 2025). At 65°C or lower, 66% of homes needed no upgrades.
Neither study can tell you about your own house. Some radiators in your home will cope at heat pump temperatures, some will need to grow, and the only way to tell them apart is to measure each room. That sum also decides how hot the heat pump has to run, and so what it costs you each winter.
Room-By-Room Heat Loss Decides It
Our lead engineer measures your house room by room before anyone talks about a model or a radiator. The heat loss calculation gives each room a figure in watts: the heat it loses through its walls, windows, floor and ceiling, and through air leaking out, on a cold design day. Set that figure against each radiator’s output at your design flow temperature and you can see which rooms are covered.
The steps on the survey run in this order:
The result goes into the written design: each radiator that stays, each one that grows, and the flow temperature it all works at. The same written design sets out the running cost, so you can see what the radiator line on the quote buys you.
The Rooms That Tend To Need A Bigger Radiator
Heat loss decides the list, so the rooms that come up are the ones that lose the most heat for their size or have the least room for a bigger radiator.
Kitchens and bathrooms
The government trial’s designers named kitchens and bathrooms most often as the problem rooms, where a large enough radiator would not fit on the walls available (Electrification of Heat report, section on barriers). Kitchen walls fill up with units and appliances. Bathrooms lose wall to tiles, the bath and the basin, and the trial found customers often chose towel rails there even though they give out less heat. A design can answer that with a taller radiator on the one free wall, a second towel rail, or underfloor loops where the floor is coming up anyway.
Outside walls and big windows
A room with two or three outside walls loses more heat than one tucked into the middle of the house. End-of-terrace gable rooms, the front room of a Victorian terrace in Sheffield or Leeds, and the top-floor rooms of Hayfield’s weavers’ houses with their long runs of mullioned windows all sit at the top of the heat loss list. A radiator sized for a boiler running hot can cover a room like that with little to spare, and at heat pump temperatures it falls short first.
Living rooms kept warmer
A living room you keep at 21°C gets less from the same radiator than a bedroom held a few degrees lower: at 50°C flow its share drops from 46% to 44%, as the note under the table shows. The design sets a target temperature for each room, so the radiator in your sitting room gets sized for the warmth you expect there.
Inner rooms that keep their radiator
A bedroom in the middle of a terrace, with one outside wall and a radiator that someone fitted generous years ago, can cover its heat loss at 50°C flow without a change. Landings and hallways with a radiator to spare can do the same. These are the radiators a careful design leaves on the wall, and leaving them there keeps the quote down.
If the wall space runs out
A radiator can grow in three directions: wider, taller, or deeper with an extra panel and more fins behind it. A double-panel radiator with fins behind each panel gives out more than a single panel of the same width. If no wall can take a bigger radiator, the options are a second radiator elsewhere in the room, a fan-assisted radiator, or underfloor heating. The trial fitted fan-assisted radiators in 18 homes, using them in small rooms short of space.
Can You Keep Microbore Pipework With A Heat Pump?
Microbore means radiator pipes narrower than the standard 15mm, often 8mm or 10mm. The catalogue rating assumes the water cools by about 20°C across the radiator (Zehnder gives the rating point as 80°C flow and 60°C return). A heat pump design lets it cool by about 5°C, the figure our table uses, so it needs about four times the flow rate to move the same heat. Push more water through a narrow pipe and it travels faster.
The Energy Saving Trust’s installer toolkit sets the acceptable water speed at 0.5 to 1.5 metres a second, with 0.9 to 1.0 as best practice, and warns that longer microbore runs hit pressure drop as well as flow rate, so the longer the run, the more likely it needs replacing (Energy Saving Trust, How to make microbore pipes work, read 13 October 2026). In the government trial, homes where microbore had to come out took around 8 to 10 days to install, against 2 to 4 days on average.
Short Tail To A Bedroom
The survey works out the flow each radiator needs at the design temperature and checks it against the pipe feeding it. A short microbore tail to a bedroom radiator can stay.
Long Run To A Living Room
A long run feeding a big living-room radiator is the one we look at hardest, because a starved radiator leaves that room cold and pushes the flow temperature up for the whole house.
Underfloor Heating With A Heat Pump
Underfloor heating suits a heat pump because it spreads heat across a whole floor and works at low water temperatures. It also takes the most disruption to fit, since the floor has to come up or a new layer has to go down, so our designs bring in underfloor loops where the heat loss figure calls for them and nowhere else.
Underfloor works best where a floor is coming up anyway: a kitchen extension, a renovated ground floor, a bathroom being refitted. Downstairs underfloor with radiators upstairs works where the heat loss supports it. The cleanest arrangement sizes the upstairs radiators to the low flow temperature the floor loops want, so the heat pump runs at one temperature for the whole house. Thick carpet and underlay hold heat back from the room, so the design asks what each floor will be covered with.
Our underfloor heating is Virotherm. The heat pump system we are proudest of runs Virotherm wet heating and cooling through the walls and ceilings of the house, low and slow, designed and fitted by our lead engineer. It is the only heat pump system we have fitted so far, and the one in our videos.
The Cost Of New Heat Pump Radiators
Average Cost Of New Emitters Per Home
The best public figures come from the same government trial. Across 687 homes that had new emitters fitted, the cost came to £2,800 a home on average, about £300 an emitter including installation, with the dearest home at £6,200 and the cheapest under £200.
What The Trial Figures Cover
- The most common number fitted was 8 to 10 emitters a home, in 38% of installs (Electrification of Heat report, Table 6 in section 7.3).
- Those prices date from installs in 2020 and 2021, and one of the three contractors left installation out of its figures.
Your figure depends on how many radiators grow, so the design keeps that count to the rooms that need it. The radiator line sits inside the full install price, and our guide to heat pump costs, install and running sets out the current government cost data for whole jobs and what pushes a quote towards the upper end.
Flow Temperature, SCOP And Your Running Cost
The radiator sizes feed into your running cost. SCOP, the seasonal coefficient of performance, measures how many units of heat the system gives back for each unit of electricity over a whole heating season. The cooler the water a heat pump has to make, the less work its compressor does and the higher the SCOP climbs. The 2025 study notes that heat pumps run at their best below 45°C, while gas boilers run at around 60 to 70°C (CIBSE Journal, January 2025).
Under Ofgem’s price cap for 1 October to 31 December 2026, electricity costs 26.32p per kWh and gas 7.97p per kWh for direct debit customers (Ofgem, Energy price cap unit rates and standing charges, read 13 October 2026). Divide one by the other and you get 3.3, the break-even SCOP: below it a heat pump costs more to run than gas, above it the heat pump wins. That sum treats your boiler as perfect; a real boiler loses some heat up the flue, so the true break-even sits a little lower. Electricity carries no VAT until 31 March 2027, and if VAT returns at today’s cap the line rises to about 3.5. Our systems are designed to a target SCOP of 3.5 to 4.0 where the house allows it, with the figure your design reaches written into your quote.
Electricity price per kWh divided by gas price per kwh equals break-even scop: 3.3 at this price cap.
You lose SCOP to undersized radiators. If one cold room needs 55°C water to reach temperature, the heat pump has to make 55°C water for the whole house, so one radiator left too small can cost you money in each room. Our engineer sets the flow temperatures and proves them against the design numbers before handover, and the yearly heat pump service rechecks the weather-compensation curve against the design.
Radiators In Stone, Brick And Post-War Semis, From New Mills To Leeds
Across our heat pump area the sum is the same, and the house type decides which rooms come up short.
In the High Peak the walls are often solid gritstone. Our heat pump installation in New Mills covers the terraces on the gorge sides near our Peak Road base, and the stone terraces of Whaley Bridge, Chapel-en-le-Frith and Mellor raise the same question of how much heat a solid wall lets through. A careful heat loss figure for those walls stops the design from either oversizing the lot or leaving the front room cold. The High Peak heat pump page covers the whole borough, and the pages for Whaley Bridge, Chapel-en-le-Frith, Mellor, Hayfield, Chinley and Furness Vale deal with each place.
Over towards Greater Manchester, the post-war semis of Marple carry radiators chosen for a gas boiler running hot, and our heat pump installation in Marple page works through which of those a design keeps. Disley mixes an old village centre with post-war estates, so two houses a street apart can need different radiator lists. Stockport’s semis and terraces sit on mains gas, which puts the running cost against gas at the centre of a heat pump installation in Stockport, and the stone houses of Glossop share the High Peak’s wall question.
We survey heat pump jobs in Sheffield and Leeds too. The Victorian terraces there carry the same front-room problem described above, and the survey and the written design work the same way.
First Point Designs It Before Quoting
You get the radiator list, the flow temperature and the running cost on paper before you commit to anything. The heat pump installation page sets out the whole process from survey to handover. For your radiators, it runs like this:
If the numbers don’t work for your house, we tell you before you spend a penny. That includes a house where the radiators, the pipes and the walls together would push the flow temperature too high to beat gas.
The grant
The Boiler Upgrade Scheme takes £7,500 off an eligible air source or ground source heat pump in England and Wales. Homes heated by oil or LPG with no mains gas connection can get an extra £1,500 until March 2027, so £9,000 in all (GOV.UK, Apply for the Boiler Upgrade Scheme: What you can get, read 13 October 2026). Grant claims run through MCS certification and ours is in progress, so ask at the survey and you get the current position. Our guide on heat pump noise, siting and planning covers the other question the survey settles: where the outdoor unit goes.
Heat Pump Radiator Questions
Do I need new radiators for a heat pump in an old stone house in the High Peak?
Some of them, and the survey tells you which. Solid stone walls lose more heat than filled cavities, so the rooms with the most outside wall tend to need a bigger radiator, while inner rooms with generous radiators often keep theirs. A room-by-room heat loss calculation names each one before the quote.
How much bigger do heat pump radiators need to be?
Going by catalogue output, a room needs about 2.2 times the rated output at 50°C flow and about 2.8 times at 45°C to match its catalogue (ΔT50) rating, using the EN 442 method in the table above. A deeper radiator with an extra panel often gets there without taking much more wall.
Are there special radiators for heat pumps?
Any wet radiator works with a heat pump if its output at your design flow temperature covers the room’s heat loss. Some makers sell models marketed as low temperature radiators. In the government trial, 57% of homes with new emitters got low temperature radiators and 33% got standard ones. Ask for the maker’s output figure at ΔT30 or lower and compare it with the room’s heat loss.
Should heat pump radiators feel hot to the touch?
No. With water at 45 to 50°C, a heat pump radiator feels warm, and it stays on for longer at that steady temperature instead of running hot in short bursts. If the room reaches its design temperature, the system is doing its job. A room that stays cold points to a radiator sized too small or a flow temperature set too low, and both show up against the design numbers.
Can I keep my microbore pipes with an air source heat pump?
Often, for short runs. The survey checks the flow each radiator needs against the pipe feeding it. Long microbore runs feeding large radiators are the ones most likely to need replacing, and the design names any that do.
Do you design heat pump radiators for homes in Stockport, Glossop, Sheffield and Leeds?
Yes. We survey heat pump jobs across the High Peak, Stockport and the edge of Greater Manchester, Glossop, Sheffield and Leeds, and the room-by-room design is the same wherever the house is.
Sources
- LCP Delta for BEIS, Electrification of Heat Demonstration Project: Home Surveys and Install Report (December 2022): https://es.catapult.org.uk/report/electrification-of-heat-home-surveys-and-install-report/ (PDF
- CIBSE Journal, How ready are UK buildings for heat pumps? (January 2025), on Childs, Bennett, Watson and Wilson, “Predicting the heat pump readiness of existing heating systems in the UK using diagnostic boiler data”
- Zehnder, Correction Factors (Delta T Conversion)
- Energy Saving Trust, Heat pump installers toolkit, How to make microbore pipes work
- Ofgem, Energy price cap unit rates and standing charges
- GOV.UK, Apply for the Boiler Upgrade Scheme: What you can get
Google Reviews From Our Customers
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Get Your Radiators Checked Room By Room
Book the free design survey and our lead engineer measures each room of your house. The written design names each radiator that stays, each one that grows and the flow temperature they work at, with the running cost and a fixed price beside it. We reply within one working day.