How Long Can a Standby Generator Run Continuously?

A home standby generator can run for as long as it has fuel and is properly maintained. That’s Generac’s own answer. In practice, there’s one important condition: Generac says its air-cooled home standby generators need a shutdown and inspection every 24 hours of continuous running, mainly to check the oil. So a Generac can carry your house through a multi-day outage, but plan on a short stop once a day.

What actually ends a long run is one of three things: fuel, oil or heat. Here’s how each one works, and what it means during an Ontario ice storm or summer heat wave.

How long can a standby generator run continuously?

There’s no fixed maximum number of days. Generac’s air-cooled 9 to 22 kW home standby generators are built for automatic backup during utility outages. When the power fails, the generator starts on its own, carries the house, and keeps going until utility power returns, as long as:

• Fuel keeps flowing. On natural gas that’s usually not a concern. On propane, it depends on the tank.
• The oil is checked and topped up. Generac’s manual says to check the oil level daily when an outage keeps the generator running for an extended period.
• The engine stays cool. The louvers need clear airflow, and the generator protects itself with automatic shutdowns if something goes wrong.

Ontario has seen what “extended” can mean. The December 2013 ice storm and the May 2022 derecho both left many homes without power for days. A properly installed and maintained standby generator is designed for exactly that kind of outage.

Natural gas vs propane: which runs longer?

Natural gas is the simplest for long outages. The fuel comes from the gas line, so there’s no tank to run dry. Generac notes that natural gas generators can often operate continuously for this reason. Most Ontario homes on natural gas are served by Enbridge Gas. A power outage doesn’t shut off the gas supply, although a gas utility shutoff, a line break or low gas pressure would still stop the generator.

Propane runs as long as the tank lasts. Generac says propane generators can run for days, depending on tank size and electrical load. Three things decide how long:

• Tank size. If a generator is converted from natural gas to propane, Generac’s manual recommends a tank of at least 250 US gallons (946 L). Generac’s support guidance also warns that other high-demand propane appliances on the same tank, like a furnace, can cause fuel supply problems.
• Load. The more of the house the generator is powering, the faster it uses fuel.
• Cold. In deep cold, a propane tank produces vapour more slowly. A tank that’s low, or too small for the load, can struggle to feed the generator even with liquid still inside.

Many rural and cottage properties in Ontario don’t have a gas line, so tank sizing deserves real planning with your installer, not a guess.

One more difference: on natural gas, Generac generators typically produce 10 to 20 percent less power than their propane rating. That’s a sizing question rather than a run-time question, but it matters when you choose a model.

Can you run a generator 24/7?

During a power outage, yes. Leave it in AUTO and it will run day and night until utility power comes back. Just plan for the daily oil check.

What a home standby generator isn’t meant for is running around the clock as your main power source. Generac’s warranty excludes using the generator in place of utility power where the utility is available, or as the primary supply where there’s no utility service at all. If you’re powering an off-grid cottage, that calls for a different kind of system.

The daily oil check during a long outage

This is the part people miss. Generac’s air-cooled engines hold very little oil, about 1 to 1.8 litres including the filter depending on the model. On a long run, checking the oil once a day is what protects the engine.

Generac’s manual describes the steps, in short:

1. Let the generator run for about one minute to cool down.
2. Turn off the main utility disconnect.
3. Turn the generator’s main circuit breaker to OFF.
4. Turn the generator off at the control panel and wait five minutes.
5. Check the dipstick and top up to the full mark with the specified oil.

The generator can start automatically and parts will be hot, so follow the full procedure in your own owner’s manual. If you’re not comfortable doing it, this is a good reason to have a service plan in place before the storm.

While the generator is off, also check that the louvers are clear of snow, ice and debris, and look for any fuel or oil leaks.

How many days until the oil needs changing?

A daily top-up isn’t the same as an oil change. On Generac’s air-cooled 9 to 22 kW models, the manual sets the oil and filter change at every 2 years or 200 hours of running. In cold weather (below 4.4 °C / 40 °F), or when the generator runs continuously in hot weather (above 29.4 °C / 85 °F), that shortens to every year or 100 hours.

In plain numbers:

• 100 hours of nonstop running is a little over 4 days.
• 200 hours is a little over 8 days.

So during an Ontario winter outage, a generator that runs for most of a week will likely need an oil change soon after, even if it was recently serviced. After any long outage, check where you are on the schedule. A maintenance plan keeps track of this for you.

Can a generator overheat?

It can, and it will protect itself. High temperature is one of the automatic shutdown alarms on Generac’s air-cooled controllers, along with low oil pressure, overload and others. If an alarm shuts the generator down, the cause needs to be fixed before it runs again.

The most common causes of overheating:

• Blocked airflow. Generac asks for at least 0.91 m (3 ft) of clear space around the intake and exhaust louvers. Shrubs, tall grass, snowbanks and ice all count.
• The wrong location. These generators are designed exclusively for outdoor installation. Enclosing one in a shed or a tight alcove cuts off the air it needs.
• Hot weather and heavy load. Generac notes that engine power may decrease above 25 °C (77 °F). A summer outage with the air conditioning running is the hardest job a generator does.

If your generator has shut down on high temperature, clear the airflow and let it cool before restarting. If it happens again, stop and book a service call.

How long can a Kohler generator run continuously?

The same principles apply to any home standby generator: fuel, oil and cooling decide how long it can run. For a Kohler, follow the intervals in Kohler’s own owner’s manual.

Getting your generator ready for a long outage

The best time to prepare is before the storm:

• Keep up with scheduled maintenance, especially the oil and battery.
• If you’re on propane, check the tank level before winter and confirm the tank is sized for your generator.
• Keep the louvers clear, and keep snow cleared around the enclosure.
• Know how to do the daily oil check, or have a service plan that covers you.

Platinum Electrical Contractors is a Generac Premier Level Dealer and a licensed electrical contractor, serving homes across Ontario from our shop in Cookstown. If your current generator can’t handle the outages you’re seeing, see our home standby generators, our monthly payment plan, or request a free quote. For more on how run hours add up over a generator’s life, read how long Generac generators last.

FAQ

How long can a standby generator run continuously?

As long as it has fuel and is properly maintained. Generac says its air-cooled home standby generators need a shutdown and inspection every 24 hours of continuous running, mainly to check and top up the oil.

Can you run a generator 24/7?

During a power outage, yes, with a short daily stop to check the oil. Running it around the clock as your main power source, in place of the utility, is outside what a home standby generator and its warranty are designed for.

How long will a generator run on propane?

It depends on the tank size, the electrical load and the temperature. Generac says propane generators can run for days. If a generator is converted from natural gas to propane, Generac recommends a tank of at least 250 US gallons (946 L).

Can a generator overheat if it runs for days?

Generac air-cooled generators shut down automatically on high temperature. Blocked louvers, snow or ice against the enclosure, and heavy loads in hot weather are the usual causes. Keep at least 0.91 m (3 ft) of clear space around the louvers.

How often should I check the oil during a long outage?

Once a day. Generac’s manual says to check the oil level daily when an outage keeps the generator running for an extended period. Shut the generator down properly first, following your owner’s manual.

Does the generator need an oil change after a long outage?

Often, yes. In cold weather, Generac’s air-cooled 9 to 22 kW models need an oil and filter change every 100 hours. That’s a little over four days of nonstop running.