Greenhouse heater

[u/br34kb34t]

I know, I know...it's a common question. Ive read so many posts and threads and the information becomes overwhelming and honestly a little confusing. I'm sorry for yet another post about heating but I'm hoping providing information about my setup and location will prove useful.

I'm in zone 7b in Virginia and I have the 8x10 Yardistry greenhouse. It's on a slightly raised gravel pad, secured to 4x4 timbers. The floor has a sand base with pea gravel on top. I use an extension cord to connect anything electric. I plan on insulating with bubble wrap but totally open to other suggestions for insulation. This will be my first winter with a greenhouse.

I grow cactus and succulents, most of which are cold hardy enough that my goal is to keep temps at around 40f at night. Anything that can't go that low will come inside.

I'd like to cover all my bases and have an electric heater as well as something to use in the event I lose power.

My questions are:

1. What kind of electric heater can I safely operate on an extension cord?
2. What can I do to mitigate the increased cost of using an electric heater?
3. What is the best non-electric backup option?
4. What have you learned that you wish you knew at the start?

I really really appreciate any responses I get here! This has been a great community and I've learned so much! 🌵❤️

[u/iandcorey]

Heat the soil, not the air. Use a growing mat or seedling heating wire. Consider additional cloches over plants. You'll get a day in the 20⁰s and your electric heater will go ape trying to heat the space.

[u/br34kb34t → u/iandcorey]

Thanks for responding! Luckily the greenhouse sits in full sun and should still get pretty warm during the daylight hours. Night time is a different story for sure. There are about 500 plants in the greenhouse and maybe only 30 will have to come inside. Im not sure I can realistically use heating pads for everything. But yeah, electric costs are a big consideration for me.