How to choose the right size and wattage of tubular heaters for your greenhouse
These aluminium Tubular Heaters are rated at approximately 60 watts per foot (30cm). The wattage of each heater available in the range is shown below:
| Heater | Length | Wattage |
| 1' | 31cm | 60w |
| 2' | 61cm | 120w |
| 3' | 91cm | 180w |
| 4' | 122cm | 240w |
Very roughly speaking, to maintain a temperature of 45 degrees Fahrenheit / 15 degrees Celcius you’ll need approximately 25 watts of power per sq. ft. of floor area. E.g. 1KW would heat approximately 40 sq.ft. (5ft x 8ft).
To calculate the heater or number of heaters you’ll require within your greenhouse is affected by several factors:
(1) The size of the greenhouse
(2) Whether the greenhouse is insulated or not
(3) The external temperature
(4) The internal temperature required.
It is therefore only possible for us to provide you with a rough guide as to the tubular heater(s) you’ll require. The table shown below shows you the wattage required to keep your greenhouse frost free – whether insulated or not insulated – and the possible combination of heaters required to achieve this:
| Greenhouse Size | Insulated | Wattage Required | Quantity / Size |
| 6' x 8' / 1.8m x 2.4m | yes | 936w | 4 x 4ft |
| 6' x 8' / 1.8m x 2.4m | no | 1170w | 5 x 4ft |
| 8' x 8' / 2.4m x 2.4m | yes | 1123w | 5 x 4ft |
| 8' x 8' / 2.4m x 2.4m | no | 1404w | 6 x 4ft |
| 8' x 10' / 2.4m x 3.0m | yes | 1310w | 5 x 4ft + 1 x 2ft |
| 8' x 10' / 2.4m x 3.0m | no | 1638w | 7 x 4ft |
| 8' x 12' / 2.4m x 3.6m | yes | 1497w | 6 x 4ft + 1 x 1ft |
| 8' x 12' / 2.4m x 3.6m | no | 1872w | 8 x 4ft |
| 10' x 12' / 3m x 3.6m | yes | 2059w | 8 x 4ft + 1 x 3ft' |
| 10' x 12' / 3m x 3.6m | no | 2574w | 10 x 4ft + 1 x 3ft |
The table above illustrates how important insulating your greenhouse can be.
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Heatsheets Insulation Easy to install you can save up to 50% of your heating costs by insulating your greenhouse. |
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Tubular Heaters have been designed to be left running constantly (and switched off when not needed) as they have an output of 60w per foot. However, by attaching a thermostat to the heater – for example our Root!t Thermostat – you’ll ensure your heaters are only run when needed to maintain the temperature you specify and will turn off and on automatically. |
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