How much will a greenhouse affect my electric bill? The cost of greenhouse utilities varies by energy source and season. For the hobby-type, it would be negligible. For the larger ones, it would depend...
For the hobby-type, it would be negligible. For the larger ones, it would depend on the rates of oil prices and such. If you started a greenhouse in March it would be a negligible amount, because heat would be the most expensive thing. Depending on your square footage, it could be anywhere from a couple of dollars to several 100 dollars per month for utilities.
You could also go with a purely solar greenhouse, in which you would gather heat from the sun during the day by capturing it in a rock bed or water source. You would then try to release that heat during the night and to help extend the season by 2-4 weeks. It is still best to have supplemental heating in case you get a severe cold snap.
