Natural gas means unlimited runtime and no tank, but a small output derate. Propane works when the gas grid fails, if the tank is sized right.
Setup Type
Quick answer: Natural gas gives a standby generator effectively unlimited runtime with no tank to fill, but most air-cooled units lose roughly 5 to 12 percent of their rated output on natural gas versus propane (est.), and they stop if the gas grid goes down. Propane works when the gas infrastructure fails and stores for years, but a large standby at half load burns roughly 2 to 3 gallons an hour, so tank size decides how many days you get. If you have a gas line and your outages are grid-only, natural gas is the low-hassle default. If you want fuel you control, or you have no line, propane earns its tank. Dual-fuel portables give you both.
Best for
Standby and dual-fuel buyers choosing a fuel before the install, especially in storm country where the gas grid itself can fail.
Wrong fit
Buyers who have not yet chosen between standby and portable, or who still need to size the unit.
Tradeoff
Natural gas trades a little output and grid dependence for never handling fuel. Propane trades tank logistics for fuel you own and can store.
Natural gas gives a standby generator effectively unlimited runtime with no tank to fill, but most air-cooled units lose roughly 5 to 12 percent of their rated output on natural gas versus propane (est.), and they stop if the gas grid goes down. Propane works when the gas infrastructure fails and stores for years, but a large standby at half load burns roughly 2 to 3 gallons an hour, so tank size decides how many days you actually get.
That is the whole decision in two sentences. The rest is matching it to your outage pattern and your property. We don't sell generators. We save you from buying the wrong one, and choosing the wrong fuel is how people end up with a generator that either can't reach its rated output or runs a tank dry three days into a week-long outage.
If you have not yet chosen standby over portable, read standby vs portable first. If you still need to size the unit, what size generator do I need comes before fuel, because the size sets how much fuel you burn.
Quick Answer: Natural Gas vs Propane at a Glance
Factor
Natural gas (NG)
Propane (LP)
Runtime
Effectively unlimited
Limited by tank size
Tank needed
No
Yes, owned or rented
Output
Baseline
Roughly 5-12% more than NG (est.)
Works if gas grid fails
No
Yes
Fuel storage life
N/A (piped)
Stores for years
Refill logistics
None
Schedule deliveries
Best for
Grid-only outages, gas line present
Grid failures, no gas line, fuel control
Both fuels run the same standby engine well. The choice is about what fails in your area, whether you have a gas line, and how many days of outage you are planning for.
Natural Gas: Unlimited Runtime, One Dependency
Natural gas is the low-hassle default, and for many homeowners it is the right call the moment they confirm a gas line reaches the unit.
The upside: no tank, no refills
A natural-gas standby is piped straight into your home's gas supply. There is no tank to install, no delivery to schedule, and no fuel to store or stabilize. When the power drops, it starts and runs, for hours or for a week, without anyone topping it off. For the buyer who wanted this handled, that is the whole appeal, and it is a real advantage. This is why natural gas is the default when the infrastructure is already there.
The derate: roughly 5 to 12 percent less output (est.)
Here is the tradeoff nobody mentions on the sticker. Natural gas carries less energy per unit than propane, so the same engine makes a bit less power on it. Most air-cooled home units lose roughly 5 to 12 percent of their rated output on natural gas versus propane (est.), and the exact figure varies by model and elevation. As an example, a 22kW propane-rated unit puts out closer to 19.5kW on natural gas (est.), which still covers a typical whole-home load with margin.
The buyer-fit read: size the generator with that derate in mind and natural gas is a fine choice, with the lost output rarely mattering. Just do not buy a unit that only clears your load on its propane rating and then run it on gas. Size for the fuel you will actually use.
The one failure mode: the gas grid
Natural gas has a single weakness, and in storm country it is not theoretical. If the event that takes your power also disrupts the gas grid, from a major earthquake, a severe freeze, or infrastructure damage, your "unlimited" fuel supply is gone. For most grid outages the gas keeps flowing and this never comes up. If you live where the gas system itself can fail, that risk is exactly why the next buyer chooses propane.
Propane: Fuel You Control, Tank Math You Own
Propane is the answer for the buyer who wants fuel they can see and store, and for anyone without a gas line. It comes with homework: the tank, and the math on how long it lasts.
The upside: works when the gas grid fails, stores for years
Propane sits in your own tank on your own property, independent of any utility. It works when the gas grid is down, and it stores for years without degrading, unlike gasoline. If your worst case is a regional event that takes gas and power together, or you simply have no natural gas service, propane keeps running. That independence is the reason to choose it.
The tank math: gallons per hour vs days of outage
This is where propane buyers get surprised, so let's do the arithmetic. A large 22kW to 24kW standby burns roughly 2 to 3 gallons an hour at half load, and most homes rarely hit full load. Tanks are filled to about 80 percent for safety, so a "500-gallon" tank holds about 400 usable gallons. Run the numbers:
Tank size
Usable (~80%)
Runtime at half load
250 gallon
~200 gal
~3-4 days
500 gallon
~400 gal
~5-8 days
1,000 gallon
~800 gal
~11-16 days
If your plan is a week-long hurricane outage, a 250-gallon tank runs dry before the lights come back, and a 500-gallon tank is the realistic floor. This calculation decides your tank, not the generator brand. Undersize the tank and you have a standby that quits mid-outage, the exact failure propane was supposed to prevent.
Tank rental vs purchase and refill logistics
You can rent or buy the tank. Renting runs roughly $100 to $200 a year and the supplier maintains it, but renters usually pay more per gallon and can only buy from that supplier. Buying a 500-gallon above-ground tank runs roughly $1,500 to $2,500 installed (underground is significantly more), and owners can shop suppliers for the best per-gallon price, with the tank paying for itself in a few years for most households. Either way, you are now scheduling deliveries and watching a gauge. For the buyer who values fuel independence, that tradeoff is worth it. For the buyer who never wants to think about fuel, it is the reason to stay on natural gas.
Dual-Fuel Portables: The Flexible Middle
If you are in the portable lane rather than standby, dual-fuel sidesteps the whole either-or. A dual-fuel portable runs on both gasoline and propane, so you get gasoline's higher output when you want it and propane's forever-storage and clean starts when you don't. Most owners store the machine on propane to dodge the stale-gas no-start, and keep gasoline as the high-output option. It is the flexible pick for a home-backup portable, and the reliability side is covered in generator maintenance cost. For specific units, see the best portable generators for home backup.
How to Choose by Your Situation
Choose natural gas if you have a gas line to the unit, your outages are ordinary grid failures, and you never want to handle fuel. Size the generator with the 5 to 12 percent derate (est.) in mind and you have the lowest-hassle backup power there is. This fits most suburban homeowners.
Choose propane if you have no natural gas service, or you live where a big event could take gas and power together, and you want fuel you control. Commit to the tank math: plan a 500-gallon tank or larger for multi-day outages, and factor in delivery scheduling. This fits rural properties and storm-belt homeowners planning for the long outage.
Choose dual-fuel if you are buying a portable and want maximum flexibility, or a machine that stores cleanly on propane but can pull higher output on gasoline. It is the practical middle for home backup that is not a whole-house standby.
Is a natural gas or propane generator better for a home?
It depends on your gas line and your outage pattern. Natural gas gives unlimited runtime with no tank and no refills, which fits most suburban homes with existing gas service. Propane works when the gas grid fails and stores for years, which fits rural homes with no gas line and anyone planning for long, severe outages. If you have a gas line and see ordinary grid outages, natural gas is the low-hassle default.
How much power do you lose running a generator on natural gas?
Most air-cooled home standby units lose roughly 5 to 12 percent of their rated output on natural gas versus propane (est.), because natural gas carries less energy per unit than propane. As an example, a 22kW propane-rated unit puts out closer to 19.5kW on natural gas (est.). The exact figure varies by model and elevation, so size the unit for the fuel you will actually run.
How long will a propane generator run on a 500-gallon tank?
A large 22kW to 24kW standby burns roughly 2 to 3 gallons an hour at half load, and a 500-gallon tank holds about 400 usable gallons at the 80 percent safe fill. That works out to roughly 5 to 8 days of runtime. A 250-gallon tank runs about 3 to 4 days, and a 1,000-gallon tank about 11 to 16 days. For a week-long outage, plan on a 500-gallon tank as the realistic floor.
Does propane last longer in storage than gasoline?
Yes, by a wide margin. Propane stores for years without degrading, while gasoline starts to break down in about a month and can varnish a carburetor within a few months without a stabilizer. That storage advantage is a big reason buyers choose propane or a dual-fuel portable.
What happens to a natural gas generator if the gas line fails?
It stops, because it has no fuel reserve of its own. For ordinary grid outages the gas keeps flowing and this is a non-issue. But in a major event that damages gas infrastructure, a freeze, an earthquake, severe storm damage, a natural gas generator can lose its supply along with the power. If you live where that risk is real, propane's on-site tank is the reason to choose it.
Should I rent or buy my propane tank?
Renting runs roughly $100 to $200 a year and the supplier maintains the tank, but you usually pay more per gallon and can only buy from that supplier. Buying a 500-gallon above-ground tank runs roughly $1,500 to $2,500 installed and lets you shop suppliers for a lower per-gallon price, paying for itself in a few years for most households. Buy if you plan to stay in the home several years, rent if you might move soon or want the supplier to own the maintenance.
Can one generator run on both natural gas and propane?
Yes, and dual-fuel is common on both standby and portable units. A standby can be configured for natural gas or propane at install, and many dual-fuel portables switch between gasoline and propane on the fly. For home backup, a dual-fuel portable is the flexible choice: propane for clean storage and long shelf life, gasoline for higher output when you need it.
Methodology
These guides are built from manufacturer documentation, public specifications, primary research where health claims matter, and repeated buyer questions that show up in real ownership and installation decisions.
Manufacturer responses can clarify pricing bands, warranty terms, support footprint, or common mistakes. They do not move a page up the shortlist on their own.
