Underfloor Heating vs Radiators for Heat Pumps
One of the most common questions homeowners ask when considering a heat pump is whether they need underfloor heating. The short answer is no — but underfloor heating does make a heat pump perform at its absolute best. Radiators can work perfectly well too, provided they are sized correctly.
This guide compares both emitter types honestly, covering efficiency, comfort, retrofit costs, and the situations where each option makes the most sense for UK homes.
Why Emitter Choice Matters for Heat Pumps
A heat pump works differently from a gas boiler. Instead of burning fuel to create heat, it moves heat from outside air (or the ground) into your home. The lower the temperature your heating system needs to operate at, the more efficiently the heat pump works.
This is measured by the coefficient of performance (COP). At a flow temperature of 35°C, a typical air source heat pump might achieve a COP of 3.5 — delivering 3.5 units of heat for every unit of electricity consumed. Push that flow temperature up to 55°C and the COP drops to around 2.2. The emitter you choose directly determines the flow temperature needed, which directly affects your running costs.
How Underfloor Heating Works with Heat Pumps
Underfloor heating (UFH) is a network of water-filled pipes embedded in or laid on top of your floor. Because the pipes cover a large surface area — essentially the entire floor — they can deliver plenty of heat at very low water temperatures, typically 30 to 40°C.
This low flow temperature is precisely what heat pumps prefer. It allows the compressor to work less hard, consumes less electricity, and keeps the system running at peak efficiency. In engineering terms, UFH and heat pumps are an ideal pairing.
Types of Underfloor Heating
There are two main types of UFH relevant to heat pump installations:
- Wet (hydronic) UFH: Warm water circulates through plastic pipes embedded in or beneath the floor. This is the type that connects to a heat pump. It is the most efficient option and the one discussed throughout this guide.
- Electric UFH: Electric heating mats or cables beneath the floor surface. These do not connect to a heat pump and run on direct electricity at a 1:1 efficiency ratio. They are useful for supplementary heating in small areas but are not a replacement for a hydronic system.
How Radiators Work with Heat Pumps
Radiators are the standard heat emitters in most UK homes. They hang on walls and transfer heat through a combination of convection (warming the air) and radiation (emitting infrared warmth). Traditional radiators were designed for gas boilers running at flow temperatures of 70 to 80°C.
Heat pumps run best at 35 to 50°C. At these lower temperatures, a standard radiator produces significantly less heat — often 30 to 50% less than its rated output. This does not mean radiators cannot work. It means they often need to be larger or upgraded to compensate.
When Existing Radiators Are Fine
If your home already has oversized radiators — common in older properties where a plumber fitted generously sized panels — they may cope perfectly well at lower flow temperatures. A heat loss calculation will confirm whether your current radiators are adequate.
When Radiators Need Upgrading
If your existing radiators are undersized for heat pump flow temperatures, you have several options:
- Replace single-panel radiators with double-panel convector (Type 22) radiators
- Add extra radiators in rooms that need more output
- Install aluminium radiators, which have better heat transfer characteristics
- Use fan-assisted radiators that boost output at lower temperatures
Comparison Table: UFH vs Radiators for Heat Pumps
| Factor | Underfloor Heating | Radiators |
|---|---|---|
| Ideal flow temperature | 30–40°C | 40–50°C (oversized) or 50–55°C (standard) |
| Heat pump efficiency (COP) | 3.0–4.0 | 2.5–3.5 (depends on sizing) |
| Comfort | Even warmth across the entire floor, no cold spots | Warm near the radiator, cooler further away |
| Responsiveness | Slow — takes 1–3 hours to warm up | Faster — 20–40 minutes to warm a room |
| Retrofit cost (per room) | £1,500–£3,500 | £300–£800 (if upgrading radiator) |
| Disruption during installation | High — floors must be lifted or built up | Low — swap panels on existing pipework |
| Aesthetics | Invisible — no wall-mounted units | Visible — takes up wall space |
| Maintenance | Very low (pipes last 50+ years) | Low (occasional bleeding, valve checks) |
| Best for | New builds, extensions, major renovations | Existing homes, room-by-room upgrades |
Retrofit Costs: UFH vs Radiator Upgrades
Retrofitting Underfloor Heating
Adding wet UFH to an existing home is possible but disruptive and expensive. The main options are:
- Screeded UFH: Pipes are laid on insulation boards and covered with a layer of screed (typically 65 to 75mm deep). This is the most effective option but raises floor levels significantly, affecting door clearances, skirting boards, and potentially stair heights. Cost: £80 to £120 per square metre including materials and labour.
- Low-profile UFH systems: Slim overlay systems (15 to 25mm total) that sit on top of the existing floor. Less disruptive but slightly less effective due to thinner coverage. Cost: £60 to £100 per square metre.
For a typical three-bedroom semi-detached house, retrofitting UFH throughout the ground floor (roughly 40 to 50 square metres) would cost between £3,000 and £6,000, plus the cost of new floor coverings. First-floor installation adds similar costs and greater complexity.
Upgrading Radiators
Replacing radiators with larger models is far simpler. A new double-panel convector radiator costs £150 to £500, and a plumber can swap one in a couple of hours. For a whole house (typically 6 to 10 radiators), budget £1,500 to £5,000 including labour.
In many cases, not all radiators need replacing. A heat loss survey will identify which rooms need larger emitters and which are already adequate.
The Hybrid Approach
Many UK heat pump installations use a combination of both emitter types. This is often the most practical and cost-effective approach:
- Ground floor: Underfloor heating where feasible (particularly in kitchens and living areas where new flooring is being laid anyway)
- First floor: Upgraded radiators (retrofitting UFH upstairs is particularly disruptive)
- Bathrooms: UFH plus a towel rail for drying towels
This hybrid setup allows the heat pump to run at a lower average flow temperature while avoiding the cost and disruption of installing UFH everywhere. Your installer can set up a blending valve so the UFH circuit runs at 35°C while the radiator circuit runs at 45°C.
Does UFH Make a Big Difference to Running Costs?
Yes, but perhaps less dramatically than you might expect. The difference in running costs between a well-designed radiator system running at 45°C and a UFH system running at 35°C is typically 10 to 20% — perhaps £100 to £250 per year for an average home.
That is a meaningful saving, but it takes many years to offset the higher cost of installing UFH in an existing home. For new builds, where UFH is installed before floors are laid, the cost premium is much smaller and the payback is faster.
New Builds vs Existing Homes
New Builds
If you are building a new home, underfloor heating is strongly recommended. The installation cost is relatively modest (pipes are laid before the screed goes down), there is no disruption to existing finishes, and you benefit from optimal heat pump efficiency for the life of the building. Most new-build heat pump installations in the UK now include UFH on the ground floor as standard.
Existing Homes
For existing homes, the decision depends on your renovation plans. If you are already lifting floors for other reasons (damp-proofing, insulation, or a major kitchen refit), adding UFH at the same time is sensible. If your floors are in good condition and you simply want to switch from a boiler to a heat pump, upgrading your radiators is usually the more practical and cost-effective route.
Frequently Asked Questions
Do I need underfloor heating for a heat pump to work?
No. Heat pumps work with both UFH and radiators. Underfloor heating allows the heat pump to operate more efficiently, but correctly sized radiators will heat your home perfectly well. Thousands of UK heat pump installations use radiators exclusively.
How much more efficient is UFH compared to radiators with a heat pump?
UFH typically allows the heat pump to run 10 to 20% more efficiently because it operates at lower flow temperatures. For an average UK home, this translates to roughly £100 to £250 per year in lower electricity bills.
Can I have underfloor heating downstairs and radiators upstairs?
Yes, this hybrid approach is very common and works well. The system uses a blending valve to supply different temperatures to each circuit — typically 30 to 35°C for the UFH and 40 to 50°C for the radiators.
How much does it cost to retrofit underfloor heating?
For a ground-floor installation in an existing home, expect to pay £3,000 to £6,000 for a typical semi-detached property. Low-profile overlay systems cost less but are slightly less efficient. New floor coverings are an additional expense.
Is electric underfloor heating worth it with a heat pump?
Electric UFH does not connect to a heat pump and is not an efficient primary heating solution. It can be useful as supplementary heating in a small bathroom or en-suite, but wet (hydronic) UFH is what pairs with a heat pump.
Will underfloor heating work with all floor coverings?
Most floor coverings are compatible, but some work better than others. Stone and tile are the most efficient conductors of heat. Engineered wood works well. Thick carpet with heavy underlay acts as insulation and reduces UFH effectiveness — if you prefer carpet, choose a thin, low-tog option.