It’s the question that matters most once a storm has passed and the grid is still dark: how long can this thing actually keep going? The honest answer depends heavily on your fuel, and the difference between the two options is bigger than most homeowners expect. Along this coast, where an outage after a named storm routinely stretches into days, runtime isn’t a spec-sheet curiosity, it’s the whole reason you’re installing standby power. Let’s do the actual math. (We connect you with one vetted, licensed local installer who’ll size all of this to your specific home, we’re the resource, not the contractor.)
Natural gas: basically unlimited
If your generator runs on natural gas piped in from a utility, the runtime question mostly disappears.
Natural gas doesn’t store at your house, it flows continuously from the utility’s distribution system, which is buried underground and largely independent of the electric grid. So as long as those pipes stay pressurized, your generator can run for days or weeks straight without you ever thinking about fuel. It’ll happily idle through a week-long restoration and keep going.
There’s a small asterisk: severe events can, rarely, disrupt gas pressure or service, and you have no on-site reserve to fall back on if that happens. But in practice, homes on a gas main in established parts of Pensacola or near Panama City can treat runtime as effectively infinite. That’s the single biggest convenience natural gas offers.
Propane: it’s tank-size math
Propane is a finite reserve sitting in a tank on your property, so here runtime is a calculation, and one worth understanding before you pick a tank.
A standby generator’s propane burn rate depends on how hard it’s working. As a rough planning guide, a mid-size air-cooled unit burns somewhere in the neighborhood of 2 to 3 gallons per hour at a heavy load, and less when the load is light. Two things affect the real number: the size of the generator and how much of its capacity your home is actually drawing at any moment. A generator rarely runs flat-out, it throttles to the load, so real-world consumption usually lands below the worst-case figure.
Now the tank side. Propane tanks are rated by water capacity, but you only fill them to about 80 percent for safety, so the usable volume is less than the sticker number:
- A 250-gallon tank holds roughly 200 usable gallons.
- A 500-gallon tank holds roughly 400 usable gallons.
- A 1,000-gallon tank holds roughly 800 usable gallons.
Put the two together. If a unit averages, say, 2 gallons an hour across a realistic day of cycling on and off, a 500-gallon tank (≈400 usable) gives you on the order of a week of run time, often more with light loads or a load-managed setup. Scale the tank up or down and the runtime scales with it. Your installer runs this same math against your actual generator size and expected load.
Sizing the tank for a multi-day outage
Here’s where Panhandle reality should drive the decision. Up north, sizing a tank for a typical outage might mean planning for a day. Here, the design target is different: a major storm can keep the lights off for the better part of a week, and after Hurricane Michael some Bay County neighborhoods waited far longer than that.
So the practical rule for propane in this region is to size the tank for the worst realistic outage, not the average one. A tank that gives you a comfortable buffer of several days, and ideally room to make it to a refill even if trucks are backed up, is the sensible target. This is exactly why homeowners around Crestview and the more rural stretches, where propane is often the only fuel option anyway, tend to go with larger tanks. It’s cheaper to buy the runtime up front than to run dry on day four.
Refills, and why timing matters
The one job propane hands you is keeping the tank fueled, and after a hurricane, that job gets harder exactly when you need it most.
Once a storm has knocked out power across the region, propane delivery trucks can be backed up for days while roads are still being cleared and demand spikes. Waiting until you’re low to call for a refill is the classic mistake. The fix is simple and it’s the single most important habit for propane owners on this coast: top off the tank before the storm, not after. Going into the season with a full tank turns a delivery bottleneck from an emergency into a non-issue. Our natural gas vs. propane guide covers this fuel-planning angle in more detail.
Oil and maintenance on a long run
There’s one more limit people forget: the engine itself needs care during a genuinely long run, and it’s independent of fuel.
A standby generator has a finite oil supply, and running it continuously for days puts real hours on the engine fast, an engine can accumulate more run time in one week-long outage than in a year of weekly self-tests. Manufacturers specify an oil-change interval in running hours, and a multi-day outage can march you right up to it. During an extended run, it’s worth checking the oil level, keeping an eye on the coolant on liquid-cooled units, and having the unit serviced once the outage ends even if the calendar says it isn’t due yet.
This is also why the condition of the unit before the storm matters so much. A generator that’s overdue for service, low on oil, or running on a weak battery is the one that quits on day three. Our maintenance guide covers the checks that keep a unit ready to go the distance.
The bottom line
On natural gas, runtime is essentially a non-question, the unit runs as long as the outage lasts. On propane, runtime is whatever you size the tank for, and the smart move here is to size it for a Panhandle-length outage and keep it topped off heading into hurricane season. Either way, the engine needs oil and attention on a long haul. When you’re ready to match a fuel, a tank size, and a generator to your home, we’ll connect you with the vetted local installer we work with, start from the hub or your city page.