Greenhouse Power Calculator

Many growers choose to heat their Greenhouse over winter to protect their plants, especially in areas where conditions are particularly harsh. 

Calculating how much power your Greenhouse needs will help determine what kind of heater to use, as well as help you individually estimate any costs for the period.

Greenhouse BTU Calculator

This section calculates the power required to heat a Greenhouse or Glasshouse structure in winter based on your input parameters.

Using the result, you can then determine how much it will cost to heat your Greenhouse over the colder months, using details from your energy provider.

This calculation is intended as a guide for estimation purposes only. Other factors like wind shear heat loss can also significantly increase heating requirements.

To use the Greenhouse heater calculator, please fill in the details then click the calculate button.


Square surface area calculator for a standard gable end Greenhouse structure

Calculate dimensions by: or

Please fill in the details below then click the calculate button.


Square Surface Area Calculator for a Lean To Greenhouse Structure

Please fill in the details below then click the calculate button.


Heat loss factor parameters

Please choose the one that most represents your structure.

Your Greenhouse heating calculator result will depend on how insulated your Greenhouse already is.

Single layer of glass
Glasshouse bubble wrap lined

How to use the Greenhouse Heating Calculator

Depending on the style of your Greenhouse, use the corresponding table below to calculate its square surface area. You will need to know the length, width, height, and eaves height of the structure. Make a note of the result.

Use the next table to work out your Greenhouse’s heat loss factor parameters, which will vary depending on whether or not your Greenhouse is bubble wrapped.

Insert the above two numbers into Greenhouse Heating Calculator, as well as:

  • the minimum outside winter night time temperature you want to protect
  • the minimum inside structure temperature you want to maintain during this period

The final number will show your Greenhouse BTU calculator result and give you an indication of how much heat your Greenhouse needs.

Note: The greenhouse heat calculator is for very approximate guidelines only. Many internal and external factors such as type of internal wrapping, walling, wind speed etc. would have an impact on the correct volume of heat power required.

For precise calculations, we recommend that a specialist heating engineer is consulted prior to equipment purchase.

How much heat does a Greenhouse need?

Our Greenhouse heating calculator will determine how much heat your Greenhouse needs to maintain a specific temperature during the cooler months. This number is dependent on a number of factors, including size of the Greenhouse, outside temperature, desire inside temperature, and current insulation. Using this information, a BTU is calculated, which is essentially how much heat your Greenhouse needs to stay a moderate temperature for your plants. This can help decide what size and style of heater is best for you.

How much does it cost to heat a Greenhouse?

While our Greenhouse heating cost calculator cannot give an exact amount on how much it will cost to heat your Greenhouse, you can use the result to determine a rough estimate.

The cost of heating a Greenhouse will vary depending on Greenhouse size and your individual energy provider. Most providers offer handy energy tables which give a guide to how much your bills will be. Use the number obtained from the Greenhouse power calculator within these tables.

What size Greenhouse heater do I need?

Determining the size of your heater depends on two things: how big your Greenhouse is and how much heat you need to generate. Of course, a more compact Greenhouse can make do with a smaller heater. A larger Greenhouse, on the other hand, will need a more powerful heater.

Our geothermal Greenhouse calculator estimates how much heat your Greenhouse will need to maintain your selected temperature. Once you have this figure, it will be easier to select the right size heater, based on the dimensions of your space and how powerful you need it to be.

Which Greenhouse heater is best?

Electric heaters are the safest and most common method of artificial heating your Greenhouse. You’ll be able to control the temperature and fans help to equally distribute the warmth. Some electric fan heaters can also be used in the summer, switching the cold setting to circulate cooler air.

Other Greenhouse heaters include propane, natural gas, and paraffin heaters. However these are best suited to smaller Greenhouses. All need to be regularly monitored and refilled.

What is the most efficient way to heat a Greenhouse?

If you already have electricity in your Greenhouse, an electric heater is the most efficient way to heat a Greenhouse and will also mostly work out to be the most cost effective too.

Propane, natural gas and paraffin heaters have a lower efficiency rating compared to electric heaters, due to the materials used and the increased loss of heat. These should therefore only be used if you don’t have electricity within your Greenhouse.