How Much Does It Cost to Run a Whole-House Generator?
Quick answer: running a whole-house standby generator costs roughly $20–$40 per day on natural gas and $100–$200+ per day on propane during continuous outage use, depending on the generator’s size and how heavily it’s loaded. On an hourly basis, that’s about $1–$2 per hour on natural gas or $4–$8+ per hour on propane. Natural gas is dramatically cheaper to run, which is why it’s the preferred fuel wherever it’s available.
Fuel is the real ongoing cost of a generator, and it surprises people — especially propane users. Here’s exactly what it costs to run one, broken down by size and fuel, plus how to keep the bill down.
Note: These are general estimates based on typical fuel prices, which vary by region and over time. Your actual cost depends on current local natural gas and propane prices and how you use the generator.
Fuel consumption by generator size
A generator’s fuel use depends on its size and load. Here’s the approximate consumption and daily cost for continuous (24-hour) operation at a typical partial load:
|
Generator size |
Natural gas use |
Propane use |
NG cost/day |
Propane cost/day |
|---|---|---|---|---|
|
7–10 kW |
~110–170 ft³/hr |
~1.0–1.5 gal/hr |
~$10–$20 |
~$60–$90 |
|
14–16 kW |
~200–250 ft³/hr |
~1.5–2.0 gal/hr |
~$22–$32 |
~$100–$140 |
|
20–22 kW |
~250–300 ft³/hr |
~2.0–3.0 gal/hr |
~$30–$40 |
~$140–$180 |
|
24–26 kW |
~300–350 ft³/hr |
~2.5–3.5 gal/hr |
~$35–$50 |
~$160–$220 |
Assumes roughly half-load average operation and typical 2026 fuel prices. Actual costs scale with how heavily the generator is loaded and local fuel rates.
Why natural gas is so much cheaper
The gap between natural gas and propane is stark — often 5x or more — and it comes down to how the fuels are priced and delivered. Natural gas is piped directly to your home and priced low per unit of energy (per therm or per 1,000 cubic feet). Propane is delivered and stored in a tank, and costs far more per unit of energy (per gallon).
For a homeowner running a generator through a multi-day outage, that difference adds up fast: a week-long outage might cost $150–$280 on natural gas but well over $1,000 on propane. This is the single biggest reason to choose a natural-gas standby generator if you have a gas line — the fuel savings over the generator’s life are substantial. We compare the fuels in detail in Propane vs Gas Generator.
How the cost actually adds up
Three things determine your running cost:
Fuel type. Natural gas vs propane, as shown above — the biggest factor by far.
Load. A generator running at 25% load burns far less than one at 90%. The more of your home you run at once, the more fuel you use. Running essentials only keeps the cost down.
Runtime. Cost is per hour, so a 6-hour outage is a fraction of a multi-day one. Most outages are short, so your typical annual fuel cost is modest — it’s the rare long outage that runs up a bill.
Put together: a typical homeowner might spend very little on generator fuel in a normal year (a few short outages), with the occasional multi-day event being the real expense — cheap on natural gas, pricey on propane.
Don’t forget the weekly self-test
Standby generators run a brief self-test automatically each week (usually 5–20 minutes) to stay ready. This uses a tiny amount of fuel — just a few cents to perhaps a dollar per week — so it’s a negligible ongoing cost, but it’s worth knowing your generator sips a little fuel even when there’s no outage.
How to reduce your running costs
Use natural gas if you can. The single biggest saving. If you have a gas line, a natural-gas generator will cost a fraction of propane to run.
Run only what you need. During a long outage, shed non-essential loads. A lightly loaded generator burns much less fuel than a fully loaded one.
Right-size the generator. An oversized generator running at low load is less efficient per kW; a properly sized unit runs in its efficient range.
Use load management. Cycling big loads keeps the generator from spiking to high fuel-burn levels.
Maintain it. A well-maintained engine runs more efficiently. Keep up with oil changes and service.
A real-world annual cost example
To put the numbers in perspective, consider a typical homeowner with a 22 kW natural-gas standby generator. In a normal year, they might see a handful of short outages totaling, say, 20 hours, plus the weekly self-tests. At roughly $1.50 an hour on natural gas, that’s about $30 in outage fuel for the year, plus a few dollars for the self-tests — call it under $50 total. Add annual maintenance (~$200–$400), and the yearly cost of owning the generator is modest.
Now imagine a bad year with a five-day outage. On natural gas, that’s roughly $30–$40 a day, or $150–$200 for the event — very manageable. On propane, the same five days could run $700–$1,000+. This is exactly why natural gas is so strongly preferred when available, and why propane users should keep the running cost in mind for long outages. Most years, generator fuel is a minor expense; it’s the rare extended outage — and your fuel choice — that determines whether the bill is trivial or significant.
Limitations and who this isn’t for
Running-cost estimates depend on fuel prices, the generator’s size and how heavily you load it, so treat any per-hour figure as a ballpark. Natural gas, propane and gasoline differ widely in cost and in availability during a crisis. Factor in maintenance and the reality that fuel can be hard to get exactly when a long outage hits.
How we source this guide: capacities, runtimes and prices are drawn from manufacturer documentation and reputable public sources and can change. Always confirm current specifications and pricing on the manufacturer’s website before buying.
Frequently asked questions
How much does it cost to run a whole-house generator per day? About $20–$40 per day on natural gas, or $100–$200+ on propane, for continuous use, depending on size and load. Natural gas is far cheaper because it’s piped in and priced low per unit of energy.
How much propane does a whole-house generator use? Roughly 1.5–3.5 gallons per hour depending on size and load — about 35–90 gallons per day of continuous operation. A large propane tank can still last several days, but the fuel cost adds up quickly.
How much natural gas does a generator use? Approximately 110–350 cubic feet per hour depending on size and load. Because natural gas is piped in and inexpensive, this typically costs just $1–$2 per hour to run.
Is it cheaper to run a generator on natural gas or propane? Natural gas, by a wide margin — often 5x cheaper per hour than propane. If you have a natural gas line, it’s almost always the more economical fuel for a standby generator.
Does a standby generator cost money when there’s no outage? Only a tiny amount. It runs a brief weekly self-test that uses a few cents to about a dollar of fuel per week. Otherwise it sits idle, consuming no fuel until an outage triggers it.
How much does it cost to run a generator during a typical year? For most homeowners with a natural-gas standby generator, very little — often under $50 in fuel for a normal year of short outages, plus annual maintenance. It’s rare multi-day outages, especially on propane, that drive up the cost.
Does running a generator on natural gas save money over propane? Yes, significantly — natural gas typically costs about 5x less per hour to run than propane. Over the generator’s life, and especially during long outages, natural gas saves substantial money where a gas line is available.
The bottom line
Running a whole-house generator costs about $20–$40 a day on natural gas or $100–$200+ a day on propane during a continuous outage — roughly $1–$2 per hour on gas versus $4–$8+ on propane. Since most outages are short, your typical yearly fuel cost is modest, with rare multi-day events being the real expense. The clearest way to keep costs down is to use natural gas if it’s available, run only your essentials during long outages, and keep the generator properly sized and maintained. Factor these running costs alongside the install price so your backup power holds no surprises.