Heat Pump Radiators 2026: What You Need to Know

Can You Keep Your Existing Radiators With a Heat Pump?

Often yes, but rarely all of them. A properly designed heat pump system will keep the radiators that are already big enough and swap the ones that aren't. In our experience looking at heat pump quotes, most three-bed homes end up replacing three to five radiators out of ten to twelve.

The rule of thumb installers use: if your existing radiator is a double-panel with fins (Type 22) and roughly the right length for the room, it probably stays. Single-panel radiators (Type 11) in medium or large rooms almost always need upgrading.

One quick check you can do yourself. Look at the side of your radiator. If you can see one flat panel, it's a single. If you can see two panels with a gap between them and finned convectors in the middle, it's a double. Doubles output roughly 60 to 70% more heat than singles of the same size.

Here's the honest bit. Some installers will tell you that you need to replace every radiator in the house. Others will tell you that you don't need to change any. Both are usually wrong. A good heat pump designer runs a room-by-room heat loss calculation and only specifies new radiators where the maths says they're too small. If your installer skips this step, get another quote.

Why Heat Pumps Need Larger Radiators Than Gas Boilers

Heat pumps produce water at a lower temperature, so each radiator needs more surface area to release the same amount of heat into the room. A gas boiler typically pushes water around your system at 65 to 75°C. A well-designed heat pump runs at 45 to 55°C, sometimes as low as 35°C in a highly insulated home.

Lower flow temperature is actually the whole point. It's what makes a heat pump efficient. Push a heat pump to run at boiler-like temperatures and its COP (coefficient of performance) collapses. You end up with an expensive electric heater rather than a proper heat pump.

The physics is simple. Heat output from a radiator is proportional to the difference between the water inside and the air in the room. Drop the water temperature by 20°C and the radiator's output roughly halves. To get the same heat into the room, you need a radiator with about twice the surface area.

That's why the industry standard for heat pump design is to size radiators to a Delta T of 30 (a 30°C difference between water and room temperature) rather than the Delta T of 50 that gas boilers assume. It sounds like jargon. In practice it just means bigger radiators, or the same-sized rooms with radiators that stick out a bit further from the wall.

We get asked whether you can just "run the heat pump hotter" to avoid changing radiators. You can. But you'll pay for it in electricity bills every winter for the next twenty years, and it's a false economy. The efficiency numbers on a properly designed system tell the story clearly.

How to Work Out If Your Radiators Need Upgrading

Get a heat loss survey done. No exceptions.

Any MCS-certified installer quoting for a heat pump under the Boiler Upgrade Scheme is required to produce a room-by-room heat loss calculation. This tells you the peak heat demand for each room in watts, and it's what determines whether your existing radiator is big enough.

The calculation looks at your walls, windows, floor, ceiling, and the target room temperature. It spits out a number like "2,400W for the lounge on a cold day". Then the installer checks your existing radiator's output at heat pump flow temperatures. If it's 1,600W, you need a bigger one. If it's 2,800W, you're fine.

You can do a rough version yourself. Search for a heat loss calculator online (Heat Geek and Heat Punk both publish free versions). Enter your rough wall areas, window types, and insulation level. It'll give you a ballpark heat loss figure per room. Then look up your radiator model and check its output at a Delta T of 30. Manufacturers like Stelrad and Kudox publish full data tables on their websites.

But honestly? This is worth paying an installer to do properly. A £150 survey now saves thousands in the wrong radiator specification later.

A couple of shortcuts that work most of the time:

• If your radiator was fitted after 2010 and it's a Type 22 double-panel, it's probably fine
• If it's a single-panel radiator in your biggest room (usually the lounge), it almost certainly needs upgrading
• Bathrooms are usually fine because heated towel rails run hot regardless of flow temperature, though very small ones may need topping up with an underfloor heating loop

Types of Radiators That Work Best With Heat Pumps

Type 22 double-panel radiators with double convectors. That's the workhorse. About 80% of heat pump installations end up using standard steel panel radiators, just larger versions of what most UK homes already have.

Type 22s are cheap (£80 to £250 depending on size), widely available, and every plumber can fit them. If you're replacing a single-panel radiator, going to a Type 22 of the same length usually gives you enough extra output without needing to make the radiator physically longer.

For rooms where wall space is tight, there are two other options worth knowing about. Fan-assisted radiators (sometimes called low-temperature radiators, made by brands like Jaga and MHS) have a small fan that boosts output without needing more surface area. They cost £400 to £900 each and use a tiny bit of electricity, but they're a good fit for retrofits where you can't extend the radiator or the wall behind it is a window.

Beyond those two, the market also includes vertical designer radiators, aluminium radiators, and cast iron for period properties, though sizing gets more complex and the price jumps considerably. Vertical radiators in particular need careful specification because tall thin radiators lose efficiency compared to horizontal ones of the same surface area.

Underfloor heating is technically the ideal partner for a heat pump because it works at very low flow temperatures (around 35°C). But retrofitting underfloor heating in an existing home costs £4,000 to £8,000 per floor, so most people stick with radiators except in extensions or full renovations. Our underfloor heating cost guide covers this in more detail.

One thing to avoid: don't mix and match too many radiator types across your system. Every radiator on the same circuit sees the same flow temperature, and mixing high-output fan radiators with normal panels can cause balancing issues where some rooms overheat while others struggle.

How Grants Like the Boiler Upgrade Scheme Can Help Cover Costs

The Boiler Upgrade Scheme pays £7,500 towards an air source heat pump or £7,500 for ground source. Radiator upgrades aren't funded as a separate line item, but they're almost always included in your installer's total quote, so the grant effectively reduces the cost of the whole package.

Here's how it works in practice. A typical air source heat pump installation on a three-bed semi runs to £11,000 to £14,000 including radiator upgrades, hot water cylinder, controls, and commissioning. The £7,500 grant is deducted from that total by your installer before you pay. You never see the grant money, it goes straight from the government to the installer. Our full heat pump grant guide walks through the application process.

If you're off the gas grid and currently on oil or LPG, the grant is £9,000 until March 2027. That's the biggest single boost to heat pump affordability we've seen, and if you're eligible, we'd genuinely push you to move on it before the deadline.

Households on qualifying benefits may also be able to fund a full heat pump switch (including radiators) through ECO4. Unlike the Boiler Upgrade Scheme, ECO4 can cover the entire cost with no contribution from you, but eligibility is much tighter. It's mostly aimed at homes with poor EPC ratings (D, E, F, or G) where the occupant receives means-tested benefits. Check the full ECO4 eligibility rules if you think you might qualify.

In Scotland, Home Energy Scotland offers interest-free loans of up to £7,500 for a heat pump plus a separate grant of up to £7,500, which stacks nicely for households upgrading radiators and heat emitters at the same time. The Scottish energy grants guide has the detail.

Warm Homes: Local Grant covers off-gas-grid homes with low EPC ratings and can also fund a full switch, though amounts vary heavily by local authority and the scheme is delivered through your council rather than direct application.

Run your postcode through our eligibility checker and it'll tell you which of these you actually qualify for based on your property and circumstances.

What to Expect From a Heat Pump Radiator Installation

Two to five days of disruption, depending on how many radiators need swapping. A full heat pump installation with radiator upgrades typically runs Monday to Friday, with the heat pump itself and hot water cylinder going in on day one or two, then radiators changed room by room over the remaining days.

Expect some mess. Old radiator swaps mean draining the system, cutting into pipework, and sometimes chasing walls where new pipes need to route differently. Reasonable installers will sheet up floors and move furniture with you. Great ones will leave your house cleaner than they found it. Ask for references from local jobs and go look at one if you can.

Before the install starts, you'll usually get a magnetic filter and a proper power flush of the whole heating system. This matters. Heat pump manufacturers void warranties if the system water quality is bad, and a flush removes the sludge that builds up over years of gas boiler use. Budget £300 to £500 for this if it's not already itemised in your quote.

After installation, the system needs balancing and commissioning. The installer will run each radiator and adjust the flow rates so every room heats evenly. This is the boring but critical bit. Ask specifically what flow temperature the system was commissioned at (you want to see 45 to 50°C for most homes, not 60°C).

One thing that surprises people: it takes a couple of weeks to get used to how a heat pump feels. Radiators are warm but not hot. Rooms heat up slowly and stay at a steady temperature rather than blasting on and off. This is normal. It's not a fault. Set the thermostat to your comfortable temperature and leave the system to run steadily, and it'll be cheaper to run than trying to boost it up and down like a gas boiler.

Check our full heat pump quote guide for what a good installation quote should include and what red flags to watch for.