The short answer
You probably do not need to replace every radiator for a heat pump, but you will likely need to change some. A heat pump runs most efficiently when it sends cooler water around the house, often 35 to 50°C instead of the 60 to 70°C typical of a gas boiler. Cooler water gives off less heat from the same radiator, so a radiator that was big enough for a boiler may be too small for a heat pump in a room that loses a lot of heat. The installer’s room by room heat loss calculation shows which radiators can stay and which need upsizing. Typical cost is £300 to £600 per radiator, fitted (checked October 2026).
Why flow temperature matters
Flow temperature is the temperature of the water leaving the heat source. A heat pump’s efficiency, measured as COP (how many units of heat it delivers for each unit of electricity), drops as flow temperature rises. Running at 45°C rather than 55°C can make a noticeable difference to running costs over a year.
The catch: a radiator’s heat output depends on how much hotter it is than the room. At lower water temperatures, each radiator gives out much less heat than its label suggests, because manufacturers rate radiators at higher boiler-style temperatures. So the job is to make the radiators big enough that low-temperature water still heats each room.
Which rooms usually need bigger radiators
The rooms that most often need an upgrade are:
- Living rooms with large windows or bay windows.
- Rooms with two or three external walls, such as corner bedrooms.
- Rooms over unheated spaces, like garages or open porches.
- Bathrooms, where a small towel rail rarely heats the room at a lower temperature.
- Rooms in extensions with large glazed doors.
Hallways and small internal rooms often keep their existing radiators.
Your options
| Option | How it helps | Trade-offs |
|---|---|---|
| Larger single panel to double panel | More surface area in the same wall space | Sticks out further from the wall |
| Double to triple panel (type 33) | Even more output from a similar footprint | Deeper, heavier, may need stronger fixings |
| A longer or taller radiator | More output from more wall area | Needs the wall space |
| Fan-assisted radiator | High output from a small unit | Needs a power supply, makes a small amount of noise, costs more |
| Underfloor heating | Very large, gentle heat source, ideal for low temperatures | Disruptive to retrofit, best done during a renovation or extension |
| Better insulation in that room | Cuts the heat the radiator needs to supply | Cost and disruption vary |
Most homes use a mix of the first three. Underfloor heating works very well with heat pumps, but retrofitting it across a whole house is a big job and rarely worth it unless floors are coming up anyway.
What the installer checks
During the survey, the installer will:
- Measure every radiator and record its type, such as single or double panel.
- Calculate each room’s heat loss at your local design temperature.
- Work out each radiator’s output at the planned flow temperature.
- Compare the two and flag any room where the radiator falls short.
- Check pipe sizes, because heat pumps need good water flow and very narrow pipes can limit it.
You should see the result as a room by room schedule. Our guide to what size heat pump you need explains the heat loss side, and how a heat pump survey works walks through the whole visit.
A quote that says “radiators as required” is not a quote. Ask for the list of rooms, the radiators being replaced and the size of each new one.
Do you need new radiators in a hybrid system?
A hybrid system pairs a smaller heat pump with a boiler, which takes over on the coldest days or for hot water. Because the boiler can run at higher temperatures when needed, a hybrid can often work with fewer radiator changes. That can suit homes where swapping radiators is difficult. See our hybrid heat pump guide for when it makes sense.
Costs in context
Radiator upgrades are part of the overall heat pump price, which typically runs £11,000 to £14,500 before grants, and £3,500 to £7,000 after the £7,500 Boiler Upgrade Scheme grant in England and Wales (typical, checked October 2026). A home needing three radiator changes is very different from one needing ten, which is one reason quotes vary. Our cost guide sets out the other factors.
Living with lower temperature radiators
Radiators on a heat pump feel warm rather than hot to the touch. That is normal. The system runs for longer at a steady, lower temperature rather than blasting heat for an hour morning and evening. Rooms stay at a more even temperature through the day. If you are used to hot radiators, it takes a week or two to trust it.
City Boiler is not an installer. We connect you with independent MCS-certified installers who size each radiator against a proper heat loss calculation and name every change in a fixed quote.
Common questions
Do I need to replace all my radiators for a heat pump?
Rarely. Most homes keep many of their existing radiators and replace a handful in rooms that lose the most heat. The room by room heat loss calculation shows exactly which ones are too small.
How much do heat pump radiators cost?
A typical radiator upgrade costs £300 to £600 each, fitted, as part of a heat pump installation (checked October 2026). Larger or designer radiators, and any extra pipework, push the figure up.
Are special heat pump radiators needed?
Not usually. Heat pumps work with ordinary steel panel radiators, as long as they are big enough. Some products are sold as heat pump radiators, such as fan-assisted models, which can help where wall space is short.
Do I need to change my pipes as well?
Sometimes. Heat pumps move more water at a lower temperature, so very narrow microbore pipes can restrict flow. Your installer checks pipe sizes during the survey and will tell you if any runs need upgrading.