Key Takeaways
- Natural gas home backup generators connect to your gas lines and can run indefinitely, as long as the pipeline stays pressurized.
- A seismic gas shutoff valve, increasingly common in California, cuts gas service during a major earthquake, disabling a natural gas generator’s fuel supply.
- Natural gas generators produce slightly less power output than the same unit running on propane, since natural gas has a lower energy density.
- Running a natural gas standby generator typically costs $20 to $50 per day, compared to $100 or more per day for the same size unit on propane.
- The 80% rule limits continuous generator load to about 80% of rated capacity, protecting the unit and extending its service life.
Estimated read: 5 min
Home backup generators for residential use come in three main fuel types: natural gas, propane, and diesel. Battery systems are a newer alternative too. Natural gas is popular because it never runs out. It isn’t automatically the best choice for every house, though. Here’s how home backup generators actually compare by fuel type.
How Natural Gas Generators Work for Home Backup
A natural gas standby generator connects directly to your home’s gas lines instead of a fuel tank. When a power outage hits, an automatic transfer switch detects it and starts the generator within seconds. The generator draws straight from the utility’s gas supply. It can keep running on natural gas for as long as the pipeline stays pressurized. That’s the core appeal of a whole-home setup like this, instead of a portable unit you manage by hand.
The Case for Natural Gas
The biggest advantage of natural gas power systems is fuel supply. There’s no tank to monitor and no fuel storage sitting on your property. There’s also no risk of running dry mid-outage, as long as the gas line stays intact. This gives most homeowners real peace of mind during long outages. That matters most during heat waves that also spike demand for air conditioning. Natural gas also tends to cost less to run than propane over a multi-day outage. It burns cleaner than diesel or gasoline too.
Standby generators fueled by natural gas tend to have a lower fuel cost per hour of generator running time. There’s no delivery truck to schedule and no tank rental fee. For homes that already have a gas line to the property, adding a generator connection is usually simpler than installing and maintaining a home backup generator on propane from scratch.
The Disadvantages of a Natural Gas Generator
Home backup generators running on natural gas aren’t perfect, though. The most significant disadvantage in California is gas line vulnerability after an earthquake. Many California homes now have a seismic shutoff valve on the house gas line, which automatically cuts off gas during significant shaking to prevent leaks and fires. That’s a good safety feature, but it also means the generator loses fuel supply at exactly the moment backup power matters most. A gas generator with no fuel supply is no better than no generator at all in that scenario.
Gas powered generators connected to a standard utility line also produce slightly less power output than the same unit running on propane. Natural gas simply has a lower energy density. A generator rated for 22 kW on propane often puts out closer to 19 to 20 kW on natural gas. That difference can matter if you’re sizing tightly around air conditioning and a sump pump running at the same time. This is exactly why choosing the right generator size for your home matters more than picking a fuel type first.
Installation cost is another factor. Running a new gas line to the generator location adds cost, especially if the meter sits far from where the unit will go. A propane tank installation doesn’t always require this extra work. And unlike portable generators, a natural gas standby unit is a permanent fixture. It isn’t something you can move, sell easily, or take with you if you relocate.
The length of a gas generator run during an outage depends mostly on whether the utility line stays pressurized. It has nothing to do with any tank you have to refill. That’s the trade worth understanding before you commit to a whole-home backup power system.
Natural Gas vs. Propane vs. Battery: Which Fits Your Home
Choosing between fuel types comes down to your specific risks and priorities.
| Fuel Type | Fuel Supply | Runs Indefinitely? | Main Consideration |
|---|---|---|---|
| Natural Gas | Utility gas lines | Yes, if the gas line stays intact | Earthquake shutoff valves can interrupt fuel supply |
| Propane | On-site storage tank | No, limited by tank size | Requires fuel storage and refilling planning |
| Battery + Solar | Solar recharge and stored energy | Yes, with enough solar capacity | No gas dependency, but depends on battery size and sunlight |
Homes in earthquake-prone areas sometimes pair a natural gas generator with a small propane backup. Some choose propane outright for that reason alone. Homes with reliable gas service and no seismic concerns often do fine with natural gas as the primary choice for their home backup generators.
Not sure which fuel type fits your home and risk profile? Copperfield Electric installs and services standby generators across Orange County. Contact us to talk through your options.
FAQ
What are the disadvantages of a natural gas generator?
The main disadvantages are gas line vulnerability after an earthquake, slightly lower power output compared to propane, and higher installation cost if the gas line run is long. A standby unit is also permanent and can’t be relocated like portable generators can.
How much does it cost to run a natural gas generator for 24 hours?
Costs vary by generator size and load. A natural gas standby generator typically runs $20 to $50 per day of continuous operation, based on typical 2026 utility rates. The same size unit on propane often costs $100 or more per day over that same period.
What is the 80% rule for generators?
The 80% rule means a generator should not be continuously loaded past about 80% of its rated capacity. Sizing a generator this way protects it from overheating. It also extends its service life, similar to how electrical code treats continuous loads on breakers. A licensed electrician factors this margin into every load calculation before recommending a generator size.
How long will a 250 gallon propane tank run a Generac?
A 250-gallon propane tank holds about 200 gallons of usable fuel after the standard 80% safety fill. For a 22kW Generac at typical outage load, that usually provides 2 to 4 days of runtime. Expect less if you’re running full air conditioning and other heavy loads continuously.
Ready to Choose the Right Home Backup Generator?
If you’re weighing home backup generators and want a straight answer for your specific home, Copperfield Electric serves homeowners across Tustin and Orange County. Call us at (626) 622-9694 or visit our contact page to schedule a consultation.
