Correct radiator output for low temperatures
Estimate a radiator’s output at heat-pump flow and return temperatures, then compare it with a room heat-loss requirement.
Method
Mean water temperature = (flow + return) ÷ 2. Corrected output = ΔT50 rating × (actual ΔT ÷ 50)^n, using n = 1.3 by default.
A 2,000 W ΔT50 radiator at 45/35/20°C has ΔT20 and produces about 608 W with exponent 1.3.
Use responsibly
Use the radiator manufacturer’s rated output and exponent where available. A room-by-room heat-loss survey and installer design are still required.
Last reviewed: 20 July 2026
Calculation and copy checked for this release.
