To put folks in the ballpark then, according to my last bill, I'm paying about .562 dollars per therm. If I multiply by 1.7 (to get to the 170,000 btu) I get .9554 dollars an hour to run a 15KW generator for an hour. But mine is 8kw, so call it about 40 percent less energy required, and my per hour cost is around .58 dollars an hour to run. Or $13.92 a day. Five gallons of gas in my old portaable generator (5kw) lasted about 12 hours. At local gas prices, that would be about 40 dollars a day. I have slightly over 110 hours on the stand-by generator so far.