That depends. How much power do you need? How many years would you amortize the upfront cost of your generator? Would you go with propane, gas, or diesel? What is your local utility rates? Would your power company allow you to disconnect from the grid? Years ago I had a place in the mountains and I went "off grid" 100%. There was an electric box on my property. The utility company tried billing me a minimum monthly rate even though I wasn't using any electric. After a long fight, where I threatened to remove their electric box with my tractor, they backed down.
Currently I have, gas, propane and diesel generators. The diesel is by far the cheapest generator to operate, for me. My propane generator is rated at 2.1 gph. My diesel uses less than 1/2 gallon per hour. I buy off road diesel in bulk. There's no tax on off road diesel.