Availability is usually the deciding factor
Natural gas requires utility service to already reach (or be extendable to) your property. Propane works anywhere, since the fuel is stored on-site in a tank rather than delivered through a utility line — this single fact narrows the decision for a lot of homeowners before cost even enters the picture.
Run-time during an extended outage
Natural gas offers effectively unlimited run-time tied to the utility supply. Propane is limited by tank size unless it's refilled during the outage — worth factoring in if your area sees multi-day outages and roads may be hard for a delivery truck to reach.
Cost tradeoffs
Propane connection setup (tank plus line) tends to cost somewhat more upfront than a natural gas line extension, and ongoing propane fuel cost is generally higher per equivalent energy unit. Natural gas is often the more economical choice long-term where it's available.
Emissions and alternative options
Both fuels are combustion-based and produce emissions, including carbon monoxide, when running — a factor some homeowners weigh alongside cost and availability. For homeowners specifically interested in zero-emissions backup power, battery-based systems (with or without solar) are a separate category worth researching, though they typically cost more upfront and offer more limited run-time than a fuel-based standby generator.
Frequently asked questions
Sources
- NFPA 54 — National Fuel Gas Code — Covers gas piping and connection requirements relevant to natural gas generator installations.
- Local utility company — Utility providers set requirements for gas meter capacity and, in some cases, generator interconnection notification.