Last verified: October 1, 2026
A home standby generator can run for days or weeks as long as it has fuel, but it is not meant to run nonstop without attention. Generac’s guidance is to shut the generator down for at least 30 minutes every 24 hours of continuous operation to check and top off the oil, and to change the oil every 200 hours (every 100 hours in extreme temperatures). A portable generator runs only as long as its fuel tank, typically several hours to about half a day, before it must be shut off and refueled.
Standby generators: the manufacturer’s rules for long outages
| Interval | What to do |
|---|---|
| Every 24 hours of continuous running | Shut down safely for at least 30 minutes; check oil and top off if needed |
| Every 200 hours since last service | Change oil (standard conditions) |
| Every 100 hours since last service | Change oil if operating below 40°F or above 85°F |
| At 400 hours | Oil and filter change, battery inspection, and air filter and spark plug replacement |
Source: Generac: Continuous use maintenance for home standby generators. Other brands publish similar guidance in their manuals; follow yours.
What that means in a real outage
- Two-day outage: one oil check after the first 24 hours.
- One-week outage in summer heat: 168 hours of running. At more than 85°F, the 100-hour oil change interval applies, so you’d need an oil change partway through the week, plus daily oil checks.
- Two-week outage after a hurricane: about 336 hours. Expect at least one oil and filter change, possibly two, and plan for it before the storm.
Keep the right oil and a spare oil filter at home before storm season. Dealers are swamped after major storms, so knowing how to do a basic oil check yourself, following the manual’s shutdown procedure, is valuable.
Fuel is the other limit
- Natural gas: effectively unlimited, as long as the utility supply continues.
- Propane: limited by tank size. A 22 kW unit at half load burns about 2.5 gallons an hour, so a 500-gallon tank lasts roughly six and a half days. See How Much Propane Does a Generator Use?
Portable generators
A portable generator’s runtime is set by its tank and load. Many mid-size models run roughly 8–12 hours at a moderate load on a full tank; check the spec sheet for your model, which usually states runtime at 25% or 50% load. Before refueling, always:
- Turn off the loads, then the generator.
- Let the engine cool; never pour gasoline onto a hot engine.
- Check the oil while it’s off: small engines can use oil over long runs.
- Keep it outdoors, more than 20 feet from the house, while running. See Generator Carbon Monoxide Safety.
A day-by-day routine for a long outage
Using Generac’s continuous-use guidance as a template, here is what a sensible routine looks like for a standby generator during a week-long outage:
| When | What to do |
|---|---|
| Every 24 hours | Safely shut down for at least 30 minutes; check oil and top off; clear vents of debris |
| Daily | Look at the controller and app for alarms; note run hours; check propane level if applicable |
| Around 100 hours in hot or cold weather (about day 4) | Oil and filter change is due under the extreme-temperature interval |
| Around 200 hours in normal weather (about day 8) | Oil and filter change due under the standard interval, counting hours since the last service |
Remember that the hour count runs from the last service, not from the start of the outage. If your generator already had 120 hours since its last oil change before the storm, an oil change could be due after only three days of continuous running in normal weather.
What a pause costs you
A 30-minute shutdown once a day means 30 minutes without generator power. Plan it: do it in daylight, when the house is cool (or warm) enough, after the fridge and freezer have been closed for a while. A full fridge stays cold for hours without power, so a short planned pause is harmless. During the pause, check the area around the unit, the fuel level and anything the app is telling you.
Portable generator runtime in practice
Portables need even more attention. Every refill means shutting down and letting the engine cool before adding fuel, then checking the oil, since small engines can consume oil over long runs. Many owners plan two or three refuelling stops a day and keep a simple log of hours, fuel and oil. Running the generator only during the hours you really need it (for example, a few hours in the morning and evening to cool the fridge and run the well pump) can stretch your fuel dramatically.
Frequently asked questions
Can a standby generator run for two weeks?
Yes, as long as the fuel lasts and you follow the manufacturer’s continuous-use routine: daily shutdowns to check oil and oil changes when the hour interval is reached.
Is it bad to shut the generator down every day?
No. Generac specifically asks for a shutdown of at least 30 minutes after every 24 hours of continuous running on its air-cooled models, so you can check and top off the oil safely.
How do I check run hours?
On the controller display or in the manufacturer’s app on connected models. Note the hours at each oil change so you know when the next one is due.
Signs your generator needs a break or a technician
- Low oil pressure or high temperature alarms.
- Unusual noises, smoke or a change in exhaust smell.
- Lights flickering or appliances behaving oddly (voltage problems).
For alarm meanings, see Generac Generator Alarms Explained, and for routine care, our maintenance checklist.