Not sure what "alternative heaters" means, but my 10 X 14 ft. greenhouse has a small "milkhouse" heater, 1500 watts, fan, and thermostat. The heater and fan work well, the thermostat not so well. I bought a separate in-line thermostat that does work. Heater price $25- $40.

I have a 240 volt electric heater from Northern Tool. My green house is 12x16. The other night it was 18 outside but 50 inside. I purposely keep it set low to save a little money. It only increased my electric bill by about $20. Not bad.

Hans

Our hydro is extremely expensive here in Ontario.

To run that 1500 watt heater would cost about $4 a day.

I shut my gh down last monday. Even though I have a natural gas heater, it would have been too expensive to keep things running.

CanadianLori I am in Ontario as well.......Niagara Falls area.

I did end up getting a small oil filled electric heater from TSC and with three setting I set it on lowest setting with thermostat set to half way keeps my greenhouse set to around 60 degrees over night.

now there is a mold issue , any advice there????

I wipe down surfaces with old towels and I also have a spray bottle full of peroxide. It takes care of mold anywhere it decides to try to show it face.

TSC heater - can you point to which one works for you? I have another smaller gh that maybe I could use this for.
many thanks
Lori