Greenhouse Heating Calculator
Heater size to hold your target temperature.
Enter your values
Results update instantly as you type — no submit needed.
Results
- Heater size needed
- 4.38 kW
- In BTU/h
- 14,961
- Temperature lift
- 18 °C
- Nightly cost at $0.25/kWh
- $13.15
Quick answer
Greenhouse heat demand depends on surface area, glazing U-value and the inside-outside temperature difference.
Watts = area × U × ΔT
How to use the Greenhouse Heating Calculator
- 1Calculate the total glazed surface area.
- 2Pick your glazing type.
- 3Enter target and coldest outside temperatures.
Frequently asked questions
Should I add bubble wrap?
Yes — internal bubble insulation can cut heat demand by a third.
Does soil store heat?
Yes, thermal mass such as water barrels smooths overnight swings.