How long can a standby generator run during an outage?

On natural gas

Natural gas comes to your home through the gas line, so there's no tank to run dry. Generac says there's no fixed maximum run time. The main things to watch are the oil level and the gas supply itself. In rare cases, very heavy demand on the gas system can reduce the gas available to your generator.

On propane

A propane generator runs off the tank on your property, so run time depends on the size of the tank, the size of the generator and how much it's powering. A generator working hard uses more fuel than one running a few circuits.

For example, Generac's spec sheet lists its 22 kW air-cooled generator at about 3.7 gallons of propane an hour at full load, and less at lighter loads. Keep in mind that propane tanks are normally filled to about 80 percent, not to the top. We size your tank with you based on how long you'd like to go between fills. Learn about propane tanks.

What Generac recommends during a long outage

For its air-cooled home standby generators, Generac recommends:

• Every 24 hours: shut the generator down for at least 30 minutes, check the oil and top it off if needed, and take a quick look around the unit. Only go out when it's safe.
• Shut it down gently: let it run without any load for about five minutes, then let it cool for another five before you work on it.
• Keep supplies on hand: have the right oil, and a spare oil filter and air filter, ready before storm season.
• After long runs: Generac calls for an oil and filter change after 200 hours of running, and more often in extreme heat or cold.

Plan before the storm

A generator that's been maintained is much more likely to run smoothly through a long outage. Our sister company, Southern Power Experts, handles yearly maintenance, so your generator is ready before the next storm. See maintenance and service plans.

Sources: Generac support articles on run time and extended outages, and Generac's air-cooled spec sheets.