Here's the honest short version: if your home already has utility natural gas, choose natural gas. It's cheaper to install, cheaper to run, and never needs a delivery truck. Propane earns its place where gas service doesn't reach — rural properties, cabins, mountain benches — and for homeowners who specifically want fuel stored on-site. Diesel is a third option for very large homes, but for most residential standby systems the real decision is gas versus propane.
The comparison at a glance
| Natural gas | Propane (LP) | |
|---|---|---|
| Fuel supply | Utility pipeline — unlimited runtime | On-site tank — runtime limited by tank size |
| Installed cost difference | Baseline; gas line run $600–$1,400 typical | Add $500–$1,800 for a tank (or lease) plus line |
| Cost per hour (mid-size home load) | ≈ $1–$3/hour | ≈ $4–$9/hour |
| 3-day outage fuel bill | ≈ $75–$200 | ≈ $300–$650 (roughly 2–3 gal/hour) |
| Storage life | N/A — always fresh | Indefinite — propane doesn't degrade |
| Works anywhere? | Only where utility gas reaches | Yes — anywhere a tank can be placed |
| Power output (same engine) | Slightly lower rating | Slightly higher rating |
| Maintenance | Essentially identical — same engines, same service schedule | |
Fuel math assumes roughly half-load operation on an 18–22 kW system at typical 2026 residential prices (natural gas ≈ $1.20–$2/therm; propane ≈ $2.50–$3.50/gallon). Your utility rates move these numbers, but the *ratio* — propane costing roughly 3× per hour — holds across most of the country.
What each choice really costs you
Natural gas: the pipeline advantage
A natural gas generator connects to the same line that feeds your furnace. The install adds a gas line run to the generator pad ($600–$1,400 for typical distances), and that's the end of your fuel logistics forever: no tank, no deliveries, no gauge to check, no runtime clock ticking during a week-long outage. For the multi-day outages that justify standby generators in the first place, unlimited runtime is a bigger deal than it sounds — a 500-gallon propane tank at half load is roughly a week of continuous power; a pipeline is indefinite.
The one caveat worth stating plainly: your generator depends on the gas utility staying up. In practice gas service survives virtually all storm-driven electrical outages — the two systems fail for different reasons. The realistic exceptions are major earthquakes and rare utility shutoffs, which is why some homeowners in seismic areas deliberately choose stored fuel instead.
Propane: energy independence, at a price
Propane works anywhere, stores forever without degrading, and burns clean. The costs are up front and ongoing: a dedicated tank (commonly 250–500 gallons for standby use) adds $500–$1,800 purchased — or a monthly lease with a delivery contract — plus code setback rules on placement, plus roughly triple the per-hour fuel cost, plus the one thing pipeline owners never think about: refill logistics during a regional emergency, when every delivery truck in the county is booked. If you go propane, size the tank for at least a week of expected use, and don't let it sit below half in storm season.
What about diesel?
Diesel units are common above 30 kW and in commercial settings — efficient and durable, but louder, with fuel that degrades in storage (stabilizers and periodic "polishing" required) and higher equipment cost ($5,000–$18,000 for the unit alone). For typical homes, gas or propane wins on simplicity.
See your cost both ways in 30 seconds
Our free calculator prices your system on natural gas or propane — same house, both fuels, side by side.
Compare My Fuel Costs →The decision framework
- Do you have utility natural gas at the house? Yes → natural gas, done. This decides it for the large majority of homeowners. (In Utah, nearly the entire Wasatch Front has gas service — see our Utah cost guide.)
- No gas service? → Propane. The tank cost is simply part of the project; get it into every quote so bids compare apples to apples.
- Have gas, but want stored fuel for earthquake/shutoff scenarios? → That's a legitimate preparedness choice; just make it knowingly, pricing the tank and the ~3× fuel cost against the peace of mind.
- Very large home, 30 kW+? → Ask bidders to price diesel alongside — at that scale it sometimes wins.
Whichever fuel you choose, remember the same engine produces slightly different output on each — a "22 kW" unit is typically rated 22 kW on propane and about 19–20 kW on natural gas. Size to the rating for your fuel (our sizing guide covers this), and make sure the installer configures and documents the unit for the fuel you're actually using.
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Licensed local installers quote your project with gas line or tank included, so there are no surprises.
Get My 3 Free Quotes →Fuel choice FAQs
Is natural gas or propane cheaper to run?
Natural gas, by roughly 3× — about $1–$3/hour versus $4–$9/hour for a mid-size home load at typical 2026 prices. Propane buys you independence from the pipeline, not savings.
Does a propane generator need its own tank?
Usually a dedicated 250–500 gallon tank (or a proper tee off a large existing one), adding $500–$1,800 or a lease. Placement must meet code setbacks from structures and property lines.
Will natural gas keep flowing during a blackout?
Almost always — gas mains don't depend on local electricity, and storm outages that take down power lines rarely touch gas service. Earthquakes and deliberate utility shutoffs are the notable exceptions.
Can one generator run on either fuel?
Most residential standby units are dual-fuel capable and can be configured for either by a technician. Output is slightly lower on natural gas — size to the rating for your actual fuel.