The answer depends entirely on fuel
“How long will it run?” is the question every Houston homeowner asks after a week without power, and the honest answer is: it depends on what you feed it. A standby generator will run as long as it has fuel and oil, the engine itself is built for it. So the real question underneath is how much fuel do you have, and how fast are you burning it. The gap between natural gas and propane on this point is enormous, so let’s take them one at a time.
First, the usual note: we’re a resource that connects you with one vetted, licensed local installer. We don’t do the work, and there’s nothing to buy here, just the runtime math you’ll want before you talk to anyone.
Natural gas: effectively unlimited
If your home fuels the generator off a natural gas line, runtime largely stops being a concern. Across much of the metro, CenterPoint Energy distributes natural gas through buried pipe, and that distribution system tends to keep flowing even when overhead power lines come down in a storm. Your generator draws from it continuously, with no tank to watch and no gauge to check.
In practice that means a natural-gas unit can run for days on end, right through the kind of multi-day outage this region actually gets. It isn’t literally infinite; the engine still needs oil service on very long runs (more on that below), and a rare pipeline disruption is possible. But for the vast majority of Houston homes on gas, “how long will it run?” is answered by “as long as the outage lasts.” That’s the quiet superpower of natural gas here, and it’s the biggest reason it’s the default fuel across the metro. The fuel overview and the full natural gas vs. propane guide go deeper on why.
Propane: it’s tank-size math
Propane is a different animal, because your fuel is finite, it’s whatever is in the tank on your property. Runtime becomes a calculation, and it’s worth understanding so you size the tank for real Houston outages rather than a best-case afternoon.
The rough mechanics: a standby generator’s propane consumption climbs with load. A common air-cooled home unit under a moderate load might burn on the order of two to three gallons per hour; push it to full load and that rises. Now put a tank behind it. A tank is typically filled to about 80 percent of its rated capacity for expansion, so a nominal 500-gallon tank holds roughly 400 usable gallons, and a 1,000-gallon tank about 800.
Do the division and the picture gets concrete. At, say, two and a half gallons an hour, 400 usable gallons is roughly 160 hours, about six and a half days of continuous running, and considerably longer if you’re managing loads rather than running everything at once. A larger tank, or a lighter load, stretches that further. These are ballpark figures, not a promise, your installer will run the numbers for your specific unit and home, but they show why the tank is the lever that controls runtime.
Sizing for a multi-day Houston outage
This is where the local reality drives the decision. Houston doesn’t get tidy two-hour outages; it gets Beryl, which left much of the metro dark for a week in July 2024, and Uri, which did the same in a freeze in 2021. If you’re on propane, you want to size the tank to outlast a realistic multi-day event without a refill, because refills are the weak link.
Two practical moves stretch any tank:
- Manage your loads. A whole-house unit doesn’t have to power everything at once. Prioritizing AC, the fridge, and a few essential circuits over, say, the pool pump and the electric range cuts your burn rate and adds days of runtime.
- Oversize the tank on purpose. Homeowners who go propane in storm country routinely choose a bigger tank than a calm-weather calculation would suggest, precisely so a hurricane week doesn’t drain it.
Deciding how many circuits you’ll actually carry ties directly into how to size a home standby generator and the sizing overview.
Refills, and why they’re the catch
The failure mode on propane is never the generator; it’s logistics. After a major hurricane, delivery trucks face the same blocked roads, fuel shortages, and demand surges as everyone else, so a tank that’s low when the storm arrives may not get topped off for days. The discipline that pays for itself: fill the tank before hurricane season, and top it off again whenever a system is in the Gulf. A full tank the day before landfall is worth more than any spec sheet. There’s more on this in the hurricane prep guide.
Oil and maintenance on the long runs
One thing both fuels share: an engine running continuously for days is doing a lot of work, and it needs oil. Standby manufacturers publish a maintenance interval, often somewhere around 150 to 200 hours of runtime, at which the oil and filter should be changed. A normal week-long outage can bump right up against that window, so on an extended run it’s worth checking oil level partway through, and scheduling service afterward. Keeping the unit maintained between events is what guarantees it’s ready to run long in the first place; the maintenance guide covers the routine, and the how it works guide explains the parts doing the running.
The bottom line
On natural gas, runtime is essentially “as long as the outage” for most Houston homes. On propane, runtime is tank size divided by burn rate, so you buy the runtime you want by sizing the tank and managing the load. Either way, an automatic standby unit outlasts a portable by a wide margin. When you’re ready to nail down the specifics for your home, we’ll connect you with our vetted local installer, start at the home page or your city page: Houston, Katy, or Conroe.