[TomatoDon]

And if the power goes out you are up a creek.

Also, and we did this some too, is get some of those inexpensive kerosene heaters. They run pretty cheap. I'm not sure the size of your greenhouse, but keresene heaters or fish cookers with bottled gas are the best for places that don't have ready access to electricity. And again, if the power goes out, you are up a creek. Also, I've seen them put a wood burning heater in a greehhouse, pipe it out the top, and the pipe even helps keep things warm all up to the top where it vents out, rather than venting it straight out the back near the wall. If you have a good access to wood, and won't be needing heat many nights, then this may be a good choice. A wood burning heater puts out the most heat, too.

Hope this helps.

Don