Underfloor heating vs radiators with a heat pump — which is more efficient (2026)
Updated: 2026-10-02 · ~2 min read
First principle: lower flow temperature = higher COP
A heat pump heats cheaper when the gap between outdoor and circuit temperature is smaller. Therefore:
- Underfloor heating works optimally at flow temperatures of 30–40 °C,
- radiators usually need 45–55 °C.
In practice the efficiency gap between the two circuits is on the order of 10–20% of annual consumption (depending on climate and insulation). It is a real, but not dominant factor — building insulation matters more than the emitter type.
Pros vs cons (table)
| Criterion | Underfloor | Radiators |
|---|---|---|
| Flow temperature | 30–40 °C → higher COP | 45–55 °C → slightly lower COP |
| Heat-up time | slow (floor mass) — stable room temperature | fast — good for second homes / weekend houses |
| Room-by-room control | limited (zones via circulation pumps) | precise, per room |
| Retrofit cost/time | requires floor work + insulation (XPS) — cost and time | cheap and fast in existing systems |
| Fit to the heat pump | optimal; a smaller buffer is usually enough | needs a well-sized buffer to avoid short cycling |
When to choose what (rules of thumb)
- New build / floor renovation → underfloor (efficiency + even heat).
- Existing radiators in good shape → keep them; add a proper buffer and set flow temperatures per the pump manufacturer.
- Mixed setup (e.g. ground floor underfloor, upstairs radiators) → two circuits with their own circulation pumps and thermostats; check how the pump’s controller handles 2 circuits.
- Emitter change after 10+ years → calculate whether insulation + new emitter really cuts the bill by as much as the floor renovation costs.
What not to do
- Do not lower radiator flow temperature “by eye” below the manufacturer’s minimum — the pump then under-heats and the backup takes over.
- Do not install underfloor without insulation (XPS) below — you lose heat into the slab/ground.
Affiliate slot: emitter/controller comparison (CPA Money2Money) — before deciding.
Sources
- Pump manufacturer guidelines (flow-temperature ranges, COP by load).
- Installer practice: buffer sizing and two-circuit control.