Standalone gasoline, diesel fuel, natural gas, or propane (LP gas) generators convert burning fuel into AC electrical power. A stationary generator can produce up to 200 kW of AC. For example, I have a 15kW stationary generator that runs on propane and backs up the utility grid power to my home. This generator provides power to my whole house should the local grid fail. Portable generators can produce 140W up to 30,000 watts of power. I also have a portable 2,000 watt gas-driven generator that provides up to amps of 120V AC. The gas tank is good for 5 to 9 hours of operation before refill. It’s been a reliable power source for camping and even for energizing field lights during school activities.