i.e a house or a hospital.
Gasoline or diesel. You can buy small generators for this. Average home would use a 2 kW typically, a 5kW if there is lots of AC and other large loads. But a hospital requires a much larger generator, and also a lot more reliablility, as well as automatic switchover. .
Diesel or propane are good for long term use on small scale. You want a generator that runs at a low RPM to give a reasonable longevity between rebuilds. A diesel engine with a large storage fuel tank would be the best for small scale power generation. If you have a pipeline source for natural gas you can run a diesel engine on natural gas or propane. What makes a diesel the best choice is that it runs at about 1200 RPM and will run possibly for years without a snag other than oil and filter changes. A gasoline engine runs closer to 4000 or more RPM which causes far more wear and friction and isn't good for long term use. Gasoline is far cheaper and good for temporary generation like for normal power outages. Natural gas or propane generators, especially ran in a diesel style engine, burn very clean and can be cheaper if you have natural gas pipelines in your area, plus you wouldn't need a storage tank for fuel. Even a 10 KW generator could go through 20 gallons of diesel a day, so you would need at least a 500 gallon tank to last a month. Pipe line would eliminate this tank and truck delivery of fuels. If you are looking at off grid power, like solar or wind, it is best to combine the two. Solar heating is the cheapest way of heating water which could be used to heat a house and/or bath water. Wind is the cheapest for DC generation of electric which is stored in big banks of lead-acid batteries. Using LCD lights and low power equipment will minimize the amount of electricity you need to generate and store
