generators for power loss

In Vermont power can go out for a few days at at time in sub zero temps during the winter.

I only need about 1000 watts tops for my set up, but an additional 1500 watts will power a small elec room heater too. So figure around 1500-3500 watts depending if I decide to go room heater or not. So...that said, I've been looking at inexpensive gererators to power my thermostates and heat tape, but have concerns about damaging my Helix thermostates.

I read about using generators that produce clean power with a natural AC sine wave for sensitive electronic equipement....is this necessary? And what small portable generator produces this? I don't have alot of cash to spend on this and want an inexpensive basic back uppower source that will cost me as little as possible. And of course I don't want to damage my thermostate or heat tape in the process. Any ideas?