Ok, then you're looking at a larger problem, generally termed co-generation; that keyword will take you down a half-million dollar plus rabbit hole...Thanks much to everyone for your replies. This is exactly the kind of "you get what you pay for" kind of advice I was hoping for! I shall present my boss with some options and see what direction I'm supposed to go.
I'm not so concerned about uninterrupted service. My main task was to come up with an alternative power source when we have a 24-hour blackout on the morning of a major show. I don't know what's up with power in this town, but there's another major outage this morning, and it's not even snowing. 2,000 customers in the dark, and the only place still running is the hospital which has.... a generator.