I have a 4600 watt generator for the herps and an inverter for the incubators. I haven't had to use the generators for my herps as the power has never gone out for more than 6 hours. The incubator is the important thing and at 30 and 50 watts they don't need much energy to run.......so the inverter lasts a long time with them.
P.S. That is the nice thing about the winter time as the boids are cooling anyways so a little dip in temp (not below 68F) won't hurt them for short periods of time (less than 12 hours).