Greenhouse heater sizing calculator
PROBTU/hr to hold greenhouse temperature on the coldest night.
Inputs
Result
BTU/hr required
17,600
Watts (electric)
5,158
The formula
BTU/hr = surface × ΔT × U-value.
Worked example
400 sq ft × 40°F × 1.1 = 17,600 BTU/hr.
Frequently asked
›Add a safety margin?
Add 20% for wind chill and infiltration.