In my Northern Tool catalog they have a 1600 running Watt generator which uses 1 gallon of gas for 3 hours of runtime or 4.8 kWh per gallon. A bigger generator uses 6 gallons of gas for 8 hours at half load (3000 Watts) or 4 kWh per gallon. A big 15kW gasoline generator uses 10 gallons to produce 6.75kW for 8 hours or 5.4 kWH per gallon.
I think the scaling would continue pretty well and especially well if you could figure out a way to distribute the power use evenly through the day in a small community. In the more limited situations of home use, you should be able to to turn down or even turn off the generator for extended periods. Even with those measures, the electricity will be quite expensive, 37 cents a kWh for the big generator with gas at $2/gallon.
A friend just left and we were talking about this subject. He suggested a diesel generator. He said an 8 or 10KW would run the whole house but....watch what you are using. Running the washing machine, micro wave and stove could be the only problems. You can also store more diesel than gas.....legally. At least in California.