Last verified: October 1, 2026
A standby generator mostly sits and waits, which is why maintenance gets forgotten until the day it fails to start. Generac’s air-cooled generators need an oil and filter change every 2 years or 200 hours, a bigger service every 4 years or 400 hours, a yearly battery check and quick owner checks, plus a pre-storm routine. In cold climates or long hot-weather runs, the oil interval shortens to every year or 100 hours. The intervals below are from Generac’s owner’s manual for its 9–22 kW air-cooled models; other brands are similar, but always follow your own manual.
The manufacturer’s schedule
| Task | When |
|---|---|
| Change oil and oil filter, check valve clearance (break-in) | After the first 25 hours of operation |
| Check oil level, fuel and oil leaks, enclosure louvers, water intrusion | Daily if running continuously, or before each use |
| Check battery condition and state of charge | Every year |
| Replace engine oil and oil filter (Schedule A) | Every 2 years or 200 hours |
| Replace oil and filter, air filter and spark plugs; inspect valve clearance (Schedule B) | Every 4 years or 400 hours |
| Oil and filter in cold (below 40°F) or continuous hot (above 85°F) conditions | Every year or 100 hours |
Source: Generac Owner’s Manual, 60 Hz air-cooled generators 9–22 kW, service schedule. The manual also says to check the oil level daily when an outage keeps the generator running for long periods. A week of continuous use is 168 hours, close to the 200-hour oil interval.
Monthly owner checklist (5 minutes)
- Controller shows Ready / Auto and no alarm lights.
- Weekly exercise ran on schedule (check the app or the controller’s history).
- Nothing blocks the air vents: leaves, snow, mulch, shrubs, wasps’ nests.
- No fuel smell, no oil on the ground, no rodent damage.
- Gas shut-off valve to the generator is open.
Dealer service
Most owners have a dealer do the scheduled services, often on a maintenance plan. Many owners book a visit every year anyway, especially in cold or coastal climates. Ask for the yearly price in writing. The visit should include:
- Oil and oil filter change when due (every 2 years or 200 hours; yearly in cold or hot-weather duty), with the oil grade the manual specifies.
- Battery test, terminal cleaning, and replacement if it fails.
- Inspection of fuel lines, wiring, the transfer switch and enclosure.
- Controller software update and error log review.
- A test run under load, if possible.
Every 4 years or 400 hours, the service adds a new air filter, new spark plugs and a valve clearance check.
Pre-storm checklist
When a hurricane or winter storm is forecast:
- Check the oil level and top up if needed. Keep a quart or two of the right oil and a spare oil filter at home for long outages.
- Propane users: confirm the tank level and order a refill early.
- Clear vents and the area around the unit; secure loose items that could blow into it.
- Confirm the controller is in Auto.
- Make sure CO alarms in the house have working batteries.
During a long outage
- Track run hours. Many owners’ manuals call for checking oil during extended operation; follow yours, and only open the unit with the engine stopped and cooled.
- Keep snow and debris away from the vents.
- Reduce big loads where possible to save fuel.
A year of maintenance, month by month
| Month | Owner task | Dealer task (if due) |
|---|---|---|
| January–February | Clear snow and ice from vents after storms; check the exercise ran | Cold-climate oil change if on the yearly schedule |
| March–April | Trim plants within 3 feet; check for rodent nests | Book spring service; battery check |
| May | Pre-storm checklist; fill propane; stock oil and filter | Complete any due service before hurricane season |
| June–November | Monthly look during the exercise; clear leaves | Post-outage oil change if hours are close to the interval |
| December | Check Daylight Saving Time and exercise schedule; note run hours | Plan next year’s service |
Keeping a maintenance log
A simple log protects your warranty and helps you spot trends. Record the date, run hours from the controller, what was done (oil, filter, battery, plugs), the oil type and quantity, and who did it. Note any alarms and how they were resolved. Keep receipts for parts and dealer invoices in the same place. Generac’s owner’s manual includes a maintenance log page for this purpose.
Signs your generator needs attention between services
- An alarm or a maintenance message (Service A or B) on the controller.
- The weekly exercise didn’t run, or took several attempts to start.
- Oil spots under the unit, or a smell of gas.
- Unusual noise, vibration or smoke during the exercise.
- Corrosion on the enclosure or connections, especially near the coast. Generac’s manual recommends periodic visual corrosion checks and washing the enclosure by hand rather than with a hose or power washer.
For alarm meanings, see Generac Generator Alarms Explained.
Frequently asked questions
How much does yearly maintenance cost?
It depends on your dealer and what’s included. Ask for a written price for each scheduled service (Schedule A and Schedule B on Generac units) and compare it with a maintenance plan. See Is a Generator Maintenance Plan Worth It?
Can I skip maintenance if the generator rarely runs?
No. Oil ages and batteries weaken even without running, which is why the schedule has time limits (2 and 4 years) as well as hour limits.
What’s the most common maintenance failure?
A weak or dead starter battery. That’s why Generac calls for a yearly battery check and why the controller shows battery warnings.
Things not to do
- Don’t spray the unit with a pressure washer or block it with covers not designed for it.
- Don’t turn off the weekly exercise to save fuel: it is how problems show up before an outage.
- Don’t open the controller or electrical compartments; leave electrical work to the dealer or an electrician.
Generator didn’t start? See Generac generator won’t start and what common alarm messages mean.