We got tired of random power failures from Detroit Edison, our mickey-mouse electric utility, and had a Generac 18-KW fully-automatic natural gas-powered standby generator installed. The automatic transfer switch disconnects from utility power when the generator fires up, and re-connects when the utility power comes back on. We don't even have to be home. Timing is everything - had it installed in June, 2003, and six weeks later we had the famous 3-day northeastern grid failure; all we had to do was reset the digital clocks . Photos at the link below.