It’s the question every homeowner asks once they get serious: if the grid stays down for a week, will my generator actually last that long? In South Louisiana, that’s not a paranoid hypothetical, it’s the exact scenario a standby system exists for. The honest answer is that runtime depends almost entirely on your fuel, and to a smaller degree on how well the unit is maintained. Let’s take those one at a time.
Natural gas: effectively unlimited
If your generator runs on natural gas piped in from the utility, there is no tank to watch and nothing to refill. The gas main feeding your home is a continuous supply, so the generator can run around the clock for as long as the electricity is out and the gas keeps flowing. And the gas usually does keep flowing, the natural-gas network is underground and separate from the overhead power lines that hurricanes tear down, so it typically survives storms that leave the neighborhood dark for days.
That’s a big part of why natural gas is so convenient in places like Orleans Parish, where Entergy New Orleans supplies gas alongside power. For a multi-day outage, “run until the grid comes back” is genuinely how it behaves. Your practical limit becomes maintenance, not fuel, which we’ll get to below.
Propane: it comes down to tank math
Propane is a different story, because your runtime is exactly however much fuel is in the tank. Once you understand that, planning gets straightforward.
A standby generator’s propane appetite scales with how hard it’s working. At a light load it sips; running your whole house through a hot afternoon with the air conditioning going, it drinks. As a rough planning figure, not a promise, since every home and unit differs, a whole-home air-cooled generator under a real household load can burn somewhere in the neighborhood of two to three gallons of propane an hour, sometimes more when the AC compressor is cycling hard in July heat. Lighter loads pull noticeably less.
Turn that into tank sizing and the picture clears up:
- A 250-gallon tank (usable capacity is less than the stamped size, since tanks fill to about 80%) might carry a busy home somewhere around a day and a half to three days, depending on load.
- A 500-gallon tank roughly doubles that window.
- Homeowners who want to ride out a long hurricane outage without thinking about it often go bigger, or run two tanks, precisely so a week-long event doesn’t mean a mid-storm refill.
The takeaway: size the tank to the outage you’re actually preparing for. In our region, that’s not a one-day thunderstorm blip, it’s the multi-day reality below.
Plan a refill for the longest events
Even a generous propane tank has a bottom. For the worst-case storms, build a simple plan before hurricane season: know your supplier, know their delivery lead time, and top the tank off when a storm enters the Gulf, not after it hits, when roads are blocked and every truck in the region is booked. A tank filled to capacity ahead of landfall buys you the most runtime and the least stress. Natural-gas homes get to skip this step entirely, which is one of its quiet advantages.
Maintenance during a long run
Fuel isn’t the only thing that limits an extended run, the engine is a machine, and running it for days straight is real duty. On long outages, keep an eye on:
- Oil. A generator running continuously for days will work through its oil the way a car on a cross-country haul does. Some units are rated for very long stretches, but during genuinely extended events an oil check (and top-off or change) may be warranted. Follow the manufacturer’s interval.
- The air filter and general health. Prolonged running under load is when a marginal component shows itself. A unit that’s been kept up on its regular maintenance is the one you want going into a week-long outage.
- The weekly self-test. A properly maintained standby exercises itself weekly precisely so you’re not discovering a problem during the storm.
None of this is a reason for alarm, it’s the difference between a generator that’s been serviced and one that’s been ignored. Which is exactly why the install and the servicing relationship matter as much as the machine.
Why this matters so much here
South Louisiana doesn’t do short outages when the big storms come. When a hurricane crosses the coast, the grid can be down for days or weeks across whole parishes at once, restoration crews can’t safely work until the winds drop and the water recedes. Houma and the bayou parishes have taken some of the longest outages in the state; Lake Charles absorbed repeated strikes in back-to-back seasons. Our power outage history lays out the pattern in detail. Runtime isn’t a spec-sheet curiosity in this region, it’s the whole reason to install permanent backup power instead of a portable and a couple of gas cans.
Next steps
- Compare the two fuels head to head: Natural Gas vs Propane
- Get the sizing right first: How to Size a Home Standby Generator
- Understand the machine itself: How a Standby Generator Works
- Ready for real numbers? We’ll connect you with a vetted local installer for a free quote, find your city.