This is an important point you must know before buying a generator. Generally, a standby generator takes 0.12 liters of petrol to generate 1kWh of power, which means it roughly uses 0.08 liters per hour to generate electricity for a small house. However, if a house's requirements are higher, it may use 0.14 liters per hour and 0.22 liters per hour for houses with high-end energy consumption.