Smarter Heating & Hot Water
Calculators / Radiator New Output

Radiator New Output

Enter the watts and the new flow, return, and room temperature. The result is the radiator output at those conditions.

Catalogue output at ΔT 50

New output
1000.00
watts
LMDT standard
49.83
K
LMDT actual
49.83
K
Correction factor
1.000
n = 1.3

Catalogue watts are the EN 442 figure at ΔT 50 (75°C flow, 65°C return, 20°C room). Output scales by (actual LMTD / that standard LMTD)1.3. Flow and return both need to sit above room temperature. See also the radiator correction factor table and BTU to watts.

Guidance only. The exponent 1.3 is a typical panel-radiator index. Check the manufacturer’s data for the emitter you are sizing, and have a qualified heating engineer confirm the design.