Guide · Costs
Underfloor heating vs radiators for a heat pump
Lower flow temperature means lower bills — but retrofitting underfloor rarely pays back.
Retrofitting wet underfloor heating costs £60–£120 per m² in a UK home, while upgrading a radiator costs £250–£500 fitted. Underfloor lets a heat pump run at 30–40°C instead of 45–50°C, which typically lifts seasonal efficiency by 10–20% (Energy Saving Trust), but the retrofit cost usually outweighs the bill saving unless floors are already coming up.
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The efficiency difference in practice
Every 5°C you drop the flow temperature adds roughly 10% to a heat pump’s coefficient of performance. Underfloor achieves the lowest flow temperatures because the emitting surface is enormous. Correctly upsized radiators at 40–45°C get most of the way there for a fraction of the cost.
Cost comparison for a 3-bed semi
- Upsizing six radiators: £1,500–£3,000.
- Ground-floor underfloor retrofit (screed, 45 m²): £3,500–£6,000 plus floor finishes.
- Low-profile overlay underfloor system: £4,000–£7,000 including door adjustments.
- New-build or extension underfloor: £45–£75 per m² — much cheaper when laid from scratch.
The practical answer for most retrofits
Underfloor downstairs where the floor is being replaced anyway, upsized radiators upstairs. That hybrid emitter approach is the most common cost-effective outcome in UK heat pump retrofits.
Frequently asked questions
- Do heat pumps need underfloor heating?
- No. Correctly sized radiators running at 40–45°C work well. Underfloor is a bonus, not a requirement.
- How much more efficient is underfloor heating with a heat pump?
- Typically 10–20% better seasonal efficiency, because the system can run 5–15°C cooler.
- Can I mix underfloor and radiators?
- Yes, and it is common — usually underfloor downstairs and radiators upstairs, zoned so each runs at its own temperature.
- Energy Saving Trust — Heat pump efficiency, running cost and SCOP benchmarks (UK).
- Nesta — How to Heat 28 Million UK Homes — Independent research on heat pump deployment and running costs.
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