Standby generator maintenance: schedule, lifespan and costs
Updated
Overview
A standby generator is an engine in a weatherproof box outside the house, wired through a transfer switch so it starts on its own when the power fails and takes over the house's circuits. It runs on natural gas or propane from the house's supply. It sits idle for most of its life, exercising itself for a few minutes each week, and then it's asked to run for days. The maintenance is a yearly service of the engine, a check of the propane tank and lines that feed it, and attention to the weekly self-test, which is the generator telling you whether it's ready.
Lifespan
A standby generator lasts 20 to 30 years. Its engine is rated in hours rather than years, and a generator in an area with few outages may use only a small share of its rated hours in its whole life. What shortens that life is neglect of the things an idle engine needs: oil that's broken down, a battery that's gone flat, fuel residue in the carburetor or injectors, and rodents nesting in the enclosure and chewing the wiring.
What extends it is the yearly service, a battery replaced on schedule rather than when it fails, and the enclosure kept clear of leaves, nests and snow. The signs a generator is near the end: self-tests it fails more than it passes, a controller that throws faults nobody can clear, an engine that burns oil or runs rough under load, and a transfer switch that's failed or is no longer made.
Maintenance schedule
The engine's service and the fuel supply's check.
| Task | How often |
|---|---|
| Service the standby generator | once a year, or after every 100 to 200 hours of run time |
| Inspect the propane tank and lines | once a year, plus a leak check with every delivery |
Replacement cost
A whole-home standby generator costs $5,000 to $15,000 installed. The range depends on the generator's output, which is sized to the circuits it has to carry, the transfer switch, the gas line work, and the concrete pad and electrical connections. A smaller unit that carries only the essentials, the furnace, the refrigerator, the well pump and a few lights, sits at the low end.
The repair-or-replace rule: a generator is a long-lived machine and most faults are repairs. A battery, a starter, a carburetor, a controller board, a set of plugs or a fuel regulator are all repairs at any age. An engine with worn rings or a failed alternator on a unit past the middle of its lifespan is where replacement starts to make sense, and the transfer switch and the pad can often be kept.
Common problems
- The weekly self-test fails: a weak battery, nearly always. Service the standby generator and replace the battery if it's older than 3 years.
- The generator cranks but won't start: no fuel reaching the engine, stale fuel residue, or a fouled plug. Check that the gas valve is open before anything else.
- The generator starts but the house stays dark: the transfer switch didn't transfer. That's an electrician's job, and a dangerous one to guess at.
- A gas smell near the enclosure or the tank: a leak. Inspect the propane tank and lines with soapy water, and call the supplier if you find bubbles.
- The generator runs rough or shuts down under load: low oil, a dirty air filter, or a fuel supply that can't keep up, which on propane can mean a tank running low or too small a regulator.
- Rodent damage in the enclosure: chewed wiring and nests. Clear the enclosure and seal the gaps they came through.
FAQ
How long does a standby generator last?
About 20 to 30 years. The engine is rated in hours, and most home generators run far fewer than they're built for. The yearly service is what gets them there.
How much does a whole-house generator cost?
$5,000 to $15,000 installed, depending on the output, the transfer switch and the gas and electrical work.
How often should a standby generator be serviced?
Once a year, or after every 100 to 200 hours of running, and after any long outage. The service is an oil change, filters, plugs and a battery check.
Why won't my generator start?
A weak battery is the usual reason, then a closed gas valve, stale fuel residue, or a controller fault. The controller's display usually says which.
Does a standby generator need professional service?
The yearly engine service can be done by an owner who's changed oil before. A professional visit adds a load test and a transfer switch check that are hard to do at home.