Drawing No. EH–TH–020 // Thermal Engineering & HVAC
Heating Coil Calculator
Reviewed August 2026
Find the sensible heating duty an air-heating coil must deliver from airflow rate and the entering/leaving air temperature rise.
What problem does this solve?
Heating coils — whether hot-water, steam or electric — raise air temperature with no moisture removal, unlike a cooling coil. Sizing one starts from the same sensible-heat relationship used throughout air-side HVAC calculations: airflow rate and the required temperature rise directly set the duty.
Inputs
Results
Background
Q [W] = 1.2 × airflow [L/s] × (Tout − Tin) [K]. This is the same air-side sensible-heat relationship used for cooling coils and general HVAC load estimates, just applied with the temperature rise going the other direction.
Hot-water coils circulate heated water through finned tubes and are common where a central boiler plant exists. Steam coils use latent heat of condensing steam and can deliver very high duty in a compact coil. Electric resistance coils convert electricity directly to heat with no water/steam distribution needed, at the cost of typically higher running cost per unit of heat versus a boiler plant.
Frequently asked questions
Practical questions about inputs, assumptions and interpretation.
No — heating alone (with no moisture added or removed) is a purely sensible process, so no humidity ratio input is needed. If humidification is also happening (common in cold, dry climates), see the separate Humidification Calculator for the additional latent load.
The duty is directly proportional to the temperature rise, so a coil serving 100% outdoor air on a cold winter design day needs far more capacity than one serving return air or a mixed airstream — this is why heating coil selection is tied closely to the outdoor design temperature for the location.
No — this is the heat delivered to the air. If the heat comes from a boiler, divide by boiler efficiency to get fuel input; see the Boiler Efficiency / Stack-Loss Calculator for that step.