A generator may or may not work with a proportional thermostat. I have one of those cheap two cycle 1000 watt generators that Lowes sold and decided to see what kind of sinewave it put out. With a light load it was all over the place and the voltage was sometimes as high as 150 volts. If you put 100 watts on it then it would settle down but the sinewave again was much more jagged than what you see from the wall. Proportional thermostats rely on the AC wave hitting zero volts for a short time in between phases and this was hit or miss with my generator so the triacs that control the AC output on a proportional thermostat would not always shut off which could cause overheating or just poor results. Again, this is a cheap (but new) generator. If I were to do it I would have a bank of marine deep cycle batteries wired in parallel with a good "pure" sine wave power inverter. Then I would use the 12VDC output of the generator to charge/maintain the deep cycle batteries. Or use solar cells for the charging. The more batteries the longer the run time between needing to charge. For just a few enclosures a single battery would do.

Or if you want to spend less you can get a Ranco/Johnson controls thermostat and use it with the generator because those are relay based and can still work on poorly regulated power. During a power outage just swap thermostats. Your temps won't be as regulated but it should keep things going.

Dion Brewington
Owner, Spyder Robotics