Florida generator guide

Natural Gas vs Propane for a Standby Generator: The Tradeoff Nobody Explains

Picture two standby generators sitting side by side. Same brand, same size steel box, same price tag. One of them will hum along for a week without a single person touching it. The other will shove more power into your house the exact moment you need it most. And you only get to feed it one fuel. So which problem do you want to have?

Get your address-specific installed price →

About five minutes. No salesman, no all-day window.

The same box turns into two different machines depending on what you feed it

Here's the thing almost nobody mentions when they hand you a brochure. Look closely at the nameplate on a whole-home generator and you'll usually find two power numbers, not one. A bigger number for propane. A smaller number for natural gas. Same engine, same day, same generator.

Why? Propane just packs more punch per puff. A cubic foot of it carries more than double the energy of a cubic foot of natural gas, so the engine gets a harder shove on every intake stroke. Feed that engine natural gas and it makes roughly five to ten percent less power. Not because it's broken. Because you handed it a lighter fuel.

Most days that gap is invisible. It shows up on the worst day, when your AC compressor, your well pump, and your fridge all lurch to life inside the same three seconds. On propane the generator barely flinches. On natural gas, a unit that was sized right to the edge can stumble on that startup surge, dip the lights, and leave you wondering why the "whole-home" generator can't quite run the whole home. The fix isn't magic. It's sizing the machine for the fuel you're actually going to burn, before it's bolted to a concrete pad in your side yard.

Natural gas "never runs out" — with an asterisk Floridians learn the hard way

The pitch for natural gas is genuinely great: a pipe runs to your house, and as long as you pay the bill, the fuel just shows up. Forever. No tank to watch, no truck to schedule. And the pipe is tougher than it sounds. It's buried underground, out of reach of the falling limbs and snapped poles that kill your electricity in the first place, and there's so much pressurized gas already sitting in the line that supply can coast for days even if something upstream hiccups.

But ask a homeowner in a storm-flattened neighborhood how that went and you'll hear the asterisk. When floodwater rips up a street, crews sometimes dig up the gas main and shut the whole block off for safety — for months, in some cases. The one time you wanted that pipe flowing is the one time a backhoe decided otherwise.

And there's a quieter Florida catch that comes before any storm: a huge number of Florida neighborhoods simply have no gas main in the ground at all. If the utility never ran a line down your street, "connect to natural gas" was never on the menu — no matter what the salesperson assumed when they pulled into your driveway.

Propane makes more power — until the day you find out you didn't fill it

Propane flips every one of those problems around. The fuel is sitting right there in a tank you own, on ground you own, answering to nobody's utility. It makes the bigger power number. It doesn't spoil sitting in the tank — a full tank you set today is still a full tank in a few years. And when a real hurricane parks over your county for two weeks, plenty of homeowners have watched a 250-gallon tank carry them the whole time and come back less than half empty, because a house running normal life never actually pulls full load.

So where's the trap? The trap is the calendar. That tank only holds what you put in it, and the delivery truck that fills it can't reach you after the storm — the same downed trees and flooded roads that killed your power are blocking the driver. Skip your pre-season top-off and you're not running your house, you're rationing it, doing mental math on the tank gauge while the storm sits there.

That's the whole tradeoff in one line. Natural gas asks you to trust a pipe you don't control. Propane asks you to remember a phone call before June.

Which one is right for your house comes down to your actual address

Notice that every real answer above bent back to one thing: where you live. Whether a gas main even reaches your street. How your ground drains. How big a propane tank your lot can hold and where the setbacks let it sit. What your AC and well pump demand in that first ugly startup second. None of that gets settled by a chart on the internet — it gets settled at your property line.

That's the part GENERasic does differently. Instead of handing you a fuzzy range and sending a salesperson to talk you upward, you put in your address and get one committed price for the generator sized to your home and your fuel — installed, permitted, and running. One number. The number you'll actually pay.

So before you flip a coin on natural gas versus propane, get the price tool to tell you what your specific house needs. Then the fuel question stops being a guess and starts being a decision you can actually make.

Common questions

If the power's out for two weeks, will my natural gas actually keep flowing the whole time?

Usually, yes — the gas main is buried and holds a lot of pressurized fuel, so it tends to outlast the electric grid it's backing up. The catch is the word 'usually.' After a severe storm or flood, utility crews will sometimes shut a gas line off for safety, and in badly hit neighborhoods that shutoff has lasted well beyond the outage itself. Natural gas is convenient, but it's a pipe you don't control. If your area has a history of gas interruptions, that's a real point in propane's favor.

How long will a propane tank really last running the whole house?

Far longer than the worst-case math on the spec sheet, because your house almost never pulls full load in an outage. Real-world, homeowners with mid-size whole-home units routinely stretch a 120-gallon tank across a couple days of hard use, and a 250-gallon tank has carried homes through two-week hurricane outages while coming back less than half empty. The single biggest lever is your load: run the essentials instead of the entire house at once and the tank lasts dramatically longer. The right tank size for you depends on how many days of outage you want to cover without a refill.

Does propane go bad just sitting in the tank between storms?

No. Propane doesn't degrade or gum up the way gasoline does — a tank you fill today is still good years from now, which is a big reason it's popular for backup power you might not touch for a long stretch. The thing that fails from sitting isn't the fuel, it's the generator itself if it never runs. That's what the weekly or monthly self-exercise cycle is for: it runs the engine long enough to burn off moisture and keep everything ready.

My street doesn't have a gas line — am I stuck?

Not at all — you're simply a propane house, and that's completely normal across a lot of Florida. Whole-home standby generators run great on propane; you just add a tank sized to how long you want to go between fills. In fact, plenty of homeowners who could tap natural gas still choose propane specifically because they'd rather own their fuel outright than depend on a utility line during the exact disaster they're preparing for.

If natural gas gets shut off during a hurricane, can the generator switch to propane?

Only if it's set up for it. A standard natural gas standby unit runs on natural gas, period — it can't magically pull from a propane tank that isn't there. Some units can be configured for propane instead, and certain models support a dual-fuel arrangement, but that's a decision made at installation, not something you flip mid-storm. If keeping a backup fuel on-site matters to you, say so up front so the system is built that way from day one.

Which fuel is actually cheaper to run during a long outage?

Natural gas is usually the cheaper fuel per unit of energy, so for a multi-week outage the running cost tends to come out lower than propane. But 'cheaper to run' is only part of the picture. Propane's cost lives up front in the tank and the fill, and its payoff is control — you own the fuel and it can't be shut off by a utility. For most homeowners the deciding factor isn't the per-day fuel cost, it's which risk they'd rather carry: a pipe they don't control, or a tank they have to remember to fill.

Stop reading ranges. Get your number.

GENERasic pulls the real property, flood, and elevation data for your exact address and returns one all-in installed price — sized to your home, your fuel, and your flood elevation. The vetted local installer confirms it on site.

Get your installed price →