How Does a Gas Generator Work?

Amber Keefer

Gas-driven electric generators can provide a back up source of power to a home or business when the main energy source fails. Connecting the generator to a transfer switch monitors electric power, and when an interruption in service occurs, it switches power to the standby generator until normal power is restored.

Backup Power

When electricity comes back on, the generator is automatically turned off. A transfer switch is actually a specialized circuit-breaker panel that is wired into a home’s regular electrical panel box as an added safety measure. Heavy-duty power cords must be used to connect a gas generator to the transfer switch or to connect appliances directly to the generator. Power cords used with generators must be able to deliver adequate wattage to power electricity to the appliances in the home.


Generators used to supply energy to a household in the event of a power loss are fairly inexpensive, typically ranging in price between $600 and $1,200 depending on the wattage you need. Generators powered by gasoline are the least expensive kind to operate, but make more noise when running. They also wear out faster than diesel, propane or natural gas generators, which can cost a lot more. To get the best price when shopping for a gas generator, you might want to consider buying from a wholesale dealer who sells products at factory direct prices (see Resources). Keep in mind that you may need to purchase accessories required for installation or extra parts should mechanical problems with the generator occur. Gas generators burn a gallon of gas about every two hours when producing a 1,000-watt output.


Before buying a generator to have on standby as a back up power source, take into account the power output, as well as how to start the generator. Some units are designed to start from a battery, and others must be manually started with a pull cord. Even generators connected to a transfer switch can be either manual or automatic. When calculating the power output you will need, allow for the number of appliances that will be running off the generator. A generator needs to produce enough wattage to power lights, as well a refrigerator, hot water heater, and perhaps a well pump, as these are usually the most essential electrical needs in a home. In most cases, a generator that puts out 5000 watts of energy will do the job. Electric heaters, air conditioning units, and even electric ranges tend to draw too much power. In order not to exceed this capacity and risk damaging the generator, turn on lights and other appliances only when they are needed to help keep power consumption down. Powering a hot water heater continuously can also put a significant strain on a generator. To determine the right size generator for your home, add up the number of watts needed to turn on lights and other electrical appliances at any one time. You can find this number on appliance labels or owner manuals. The size generator you choose should be slightly larger than the wattage you need to handle the load. Consider, too, that it takes more energy to start up a generator.

Safe Fuel Tips

Because the shelf life of gasoline is somewhat short, it should not be stored for more than several weeks unless a stabilizing chemical is added. The best thing to do is to routinely rotate the fuel you have on hand. When it is time to refill the fuel tank, turn off all electrical equipment in the house, shut off the generator, and then allow it to cool before adding more fuel to the tank. Drain the gas tank when the generator is not being used. If a generator is powered by natural gas, shut off the valve at the gas line and run the generator until it stops to burn any gas remaining inside the engine. To reduce the risk of carbon monoxide poisoning, locate portable generators at least 10 feet away from the home. You may have to check with local zoning and building codes in your area.