Greenhouse Heating Calculator: How Much Heat Does Your Greenhouse Need?
Heating a greenhouse is a volume and temperature problem. This calculator estimates the watts from size and the gap you need to hold.
What is the Greenhouse Heating Calculator?
A greenhouse heater must replace the heat lost through its air and surfaces. Enter the greenhouse size and the inside-outside temperature gap, and this tool estimates the watts needed with a simple volume-based rule. This is an estimate for planning, not a heating engineer's specification.
How to use it
- Enter your values in the fields provided.
- Click Estimate Heating Power.
- Read the result and adjust an input if you want a different outcome.
Worked example
A 10 by 5 by 3 metre greenhouse with a 15 C gap needs an estimated 2700 watts, or 2.7 kW.
How much heating does a 10 by 5 by 3 metre greenhouse need over a 15 C gap?
The volume is 150 cubic metres, and 150 times 15 times 1.2 gives 2,700 watts, or 2.7 kW, as a planning estimate.
Frequently asked questions
What do I enter to get a result?
Fill in every field with your own numbers or choices, then run the tool. Empty number fields count as zero, so check them before you trust the output.
Can I reuse this result elsewhere?
Yes. The result is calculated in your browser from the values you entered, so you can copy the numbers into your own notes or plan.