Greenhouse Heating Systems

Perhaps no other greenhouse decision will create more anxiety than deciding on your choice of heating system. The fact is, most greenhouses cost less to heat than homeowners expect, and you have several options that will work well. With the rising cost of natural gas and propane, the cost to run gas or electric heaters are about the same. Some things to consider:

Electric heaters are nearly 100% efficient in converting input energy (kilowatts) into heat output. Our compact 240 volt electric heaters operate at lower amperage than 110 volt heaters and are very efficient and reliable.

Gas heaters are only 80% efficient, so you need to figure for extra capacity (BTU output) and order a unit sized accordingly.

Electric heaters do not require any exhaust or air intake flues and can be conveniently located under a potting bench or hanging from a gable endwall.  Most gas heaters require a flue pipe to remove gas exhaust fumes, or an air intake vent to provide fresh oxygen to burn. Both allow cold air to enter your greenhouse and require a 3-4 inch hole through the wall at some location.

BTU Calculator

Sq. Ft. Exposed Surface Area x ( Tmax – Tmin ) ÷ R
Square Feet of Glass or Poly Surface Area x ( Maximum Temperature Inside – Minimum Temperature Outside ) ÷ R-value

R-Values
Glass - Single Pane - 1.0
Polyethylene - Double Layer - 1.5
Polycarbonate - 8mm Twinwall - 1.6
Glass - Double Pane - 2.0