HEAT LOSS HUB · TOOLBOX
Radiator Output Calculator
Radiator output changes considerably as heating system temperatures are reduced. A radiator that provides sufficient heat when connected to a traditional boiler may provide significantly less heat when used with a heat pump or other low-temperature heating system.
Use the calculator below to estimate radiator output at different operating temperatures.
Understanding radiator output
Radiator manufacturers normally publish outputs at a specified temperature difference, often referred to as ΔT or Delta T. When the average water temperature through the radiator is reduced, its heat output also reduces.
This is particularly important when assessing existing radiators for heat pumps, where lower flow temperatures can improve efficiency but may require larger radiators.
Important
This calculator is intended as a useful estimation and educational tool. Actual radiator performance can vary between manufacturers, models and installation conditions.
For final heating system design or radiator selection, manufacturer data and an appropriate room-by-room heat loss calculation should be used.
Need an accurate heat loss calculation?
Understanding radiator output is only part of heating system design. Heat Loss Hub provides independent heat loss calculations and heating system design support.