In short: a standby generator needs a professional service at least once a year, plus a weekly self-test it runs on its own. Generac’s schedule: first oil change after 25 hours, then every 200 hours or 2 years (yearly in extreme heat or cold). Most no-starts come from a closed fuel valve, low propane or a weak battery.
A generator that sits for months and then has to run for three days straight needs care in between. This page covers the maker schedules, what a service visit should include, the faults you can check yourself, when to call a pro, what service plans cost and how to pick a technician.
Generator maintenance at a glance
- Weekly: the generator exercises itself for a few minutes. Kohler says to run it weekly; Generac’s 22 kW runs a 5-minute test. Glance at the status light.
- Every year: professional service. Kohler says most standby generators should be serviced “at least once per year,” even without outages. Generac recommends service every 6 months by an authorized dealer.
- By hours: oil after the 25-hour break-in, then every 200 hours or 2 years; air filter and spark plugs every 400 hours or 4 years (Generac).
- Battery: typically lasts 3 to 5 years (Generac support).
- Typical cost: about $80 to $300 a year for maintenance (HomeAdvisor, 2026).
Maker maintenance schedules
Always follow your own owner’s manual first: intervals differ by model, and keeping to them can matter for the warranty. Here is what the two biggest home standby brands publish.
| Task | Generac home standby | Kohler (Rehlko) home generators |
|---|---|---|
| Exercise | Automatic weekly or set schedule; 5-minute test on the 22 kW | Weekly; test remote operation monthly |
| Break-in oil change | After the first 25 hours of run time, however they were reached | Per manual |
| Oil and filter | Every 200 hours or 2 years; every 100 hours or yearly below 40°F or above 85°F | Oil yearly or every 100 hours; filter yearly or every 200 hours |
| Air filter, spark plugs | Every 400 hours or 4 years | Inspected at annual service |
| Battery | Inspect every 2 years or 200 hours; typical life 3 to 5 years | Tested at annual service |
| Professional service | Every 6 months by an authorized dealer (Generac FAQ) | At least once a year |
Why the 25-hour break-in matters: Generac says it is required by engine hours, not calendar time, because it “protects the engine during its initial wear-in period.” A long outage can use up those hours in a day or two, so plan the first service soon after a big storm.
What a service visit should include
Kohler lists the usual annual visit: engine oil and filter, air filter inspection or replacement, spark plug inspection, battery test, fuel system inspection, electrical connection checks, control panel diagnostics and a full operational test. Ask for a written checklist with the hours on the meter and the battery reading. A healthy 12-volt starting battery reads about 12.6 volts fully charged, according to Generac.
Between visits, you can keep the area clear of leaves, snow, mulch and plants, make sure nothing blocks the air vents, look for animal nests, check that propane is above the level your dealer recommends and confirm the unit is in AUTO after any work.
During a long outage
Standby generators are built to run for days, but not without a pause. Generac says its air-cooled home units should be shut down for at least 30 minutes after every 24 hours of continuous running, so the oil can be checked and topped off, the fuel lines and connections inspected for leaks, and dirt or debris cleared from the louvers. Check the run-hour counter on the control panel or the app: a three-day outage adds about 72 hours, which can bring the first 25-hour service or the 100-hour hot-climate service due. Keep the service records; Generac says they matter for the warranty. If you aren’t comfortable doing the daily check, ask your dealer to show you at the next visit.
Common faults and what to check
Generators show an alarm or a colored light when something is wrong. These are the ones owners see most in Generac’s support guide. Check the simple things; leave anything inside the enclosure to a technician.
| Symptom or alarm | Likely cause | What you can do |
|---|---|---|
| Overcrank (engine cranks but won’t start) | Fuel valve off, low propane, gas supply problem | Check that the fuel shutoff valve is on and the propane tank has fuel; clear the alarm as the manual says; set to AUTO. If it returns, call a dealer. |
| Low battery | Battery discharged or failing; charger issue | Generac says to allow a full 24-hour charge cycle; the unit needs at least 12 volts to start. Replace batteries that won’t hold a charge. |
| RPM sense loss | Often battery if the engine won’t crank; otherwise a sensor or engine fault | Call a dealer. |
| Didn’t start in an outage | Unit not in AUTO, an active alarm, a blank control panel (battery, fuse), or the transfer switch not switching over | Check the mode and the app or control panel for alarms. Never work on the transfer switch yourself. |
| Starts when the power is on | Scheduled exercise, a brownout (utility voltage too low), an alarm, or the transfer switch position | Check the exercise time and alarms; if it repeats, call a dealer. |
Call a professional for oil or coolant leaks, smoke, knocking, repeated alarms, any gas smell (leave the area and call the gas utility from outside), water inside the enclosure after a flood, or any problem with the transfer switch. Generac says only its authorized service dealers can do warranty work.
Portable generators: the owner’s checklist
Portable generators are usually maintained by their owners. Follow the manual for oil changes (they come often on small engines), check the oil before each use and run the generator for a short time every month or so. Stale gasoline is the most common reason a portable won’t start after storage: treat stored fuel with a stabilizer (STA-BIL says its Storage formula keeps fuel fresh for up to 24 months) or drain it as the manual says. Test your CO alarms monthly. Our generator safety guide has a printable outage checklist.
Safety while you check or run a generator
- Run portable generators outdoors only, at least 20 feet from the house, exhaust away from windows, doors and vents; never in a garage, basement, shed or porch, even with doors open (CPSC).
- CPSC says nearly 100 people die each year in the U.S. from carbon monoxide from portable generators. Keep battery or battery-backup CO alarms on every level of the home.
- Turn the generator off and let it cool before refueling (Ready.gov).
- A standby generator can start by itself. Before anyone touches it, it should be switched off and disconnected as the manual says. That is a job for the technician.
Service plans and what maintenance costs
Many dealers sell yearly or twice-yearly service plans. HomeAdvisor’s 2026 data puts generator maintenance at about $80 to $300 a year; repairs are priced separately. When you compare plans, ask:
- How many visits a year, and what is on the checklist?
- Are oil, filters, spark plugs and the battery included, or billed as parts?
- Do plan customers get priority during storms? Is there an emergency call-out fee?
- Is the technician authorized by your generator’s brand, so warranty repairs are covered?
- Does the plan renew automatically, and how do you cancel?
Remote monitoring (Wi-Fi apps from the makers) can alert you to a low battery or a missed exercise before an outage. It’s useful, but it doesn’t replace the yearly service.
Businesses: maintenance rules are stricter
Commercial and life-safety generators often fall under NFPA 110, the standard for emergency and standby power systems, which sets inspection, exercise and testing routines; industry guides summarize them as weekly inspections and monthly exercise under load. Diesel engines also fall under EPA’s stationary engine rules, which limit maintenance and testing hours and require records. Your inspector or fire marshal decides what applies. See commercial backup generators.
How to choose a generator technician
- Brand authorization: check the maker’s dealer locator (Generac, Kohler, Briggs & Stratton) for warranty work.
- License: electrical work on the transfer switch or wiring needs a licensed electrician. Look them up on your state’s site; each state page links the board, for example Florida or Texas.
- Insurance and a written estimate before repairs.
- Red flags: “replace everything” without diagnosis, a cash-only demand, a service plan that won’t say what’s included, or pressure to buy a new unit when a repair hasn’t been priced. If you sign a contract at home, the FTC’s Cooling-Off Rule usually gives you three business days to cancel sales of $25 or more.
Thinking of replacing an old unit instead? Read standby generator installation and whole house generator cost.
Get help with your project
Tell us your generator’s brand, size and age and what’s wrong, or that you want a maintenance plan. Tell us about your project and we will connect you with a licensed, independent installer who serves your area. It is free, there is no obligation, and only the installer you choose gets your details. See how it works.
Generator maintenance questions
How often should a standby generator be serviced?
At least once a year, says Kohler, even if you had no outages; Generac recommends a dealer service every 6 months. By hours, Generac calls for an oil change after the first 25 hours, then every 200 hours or 2 years, and yearly in very hot or cold climates. After a long outage, book a service sooner.
Why won’t my generator start during an outage?
The usual causes are simple: the unit isn’t in AUTO, the fuel valve is closed, the propane is low or the battery is weak. Generac’s overcrank alarm means it cranked but didn’t start; check the fuel valve and tank first. A low-battery alarm needs a full 24-hour charge. If an alarm keeps returning, call an authorized dealer.
How much does generator maintenance cost?
HomeAdvisor’s 2026 data puts it at about $80 to $300 a year. Dealer service plans vary by visits, parts included and storm-priority service, so compare what each covers. Repairs, a new battery or work after a flood are usually extra. Ask for a written checklist of what each visit includes before you sign.
How long does a generator battery last?
Typically 3 to 5 years, according to Generac’s support guidance. Heat, cold and long idle periods shorten it. Generac says a fully charged 12-volt starting battery reads about 12.6 volts. Have the battery tested at every service, and replace it before storm season if it is near the end of its life or fails a load test.
Can I service my own standby generator?
Owners can keep the area clear, watch the status light and check propane. Oil changes and repairs are better left to an authorized technician: the unit can start by itself, it connects to your gas line and electrical panel, and Generac says only its authorized dealers can perform warranty work. Check your warranty terms before doing any service yourself.
Sources
Maintenance schedules, break-in, battery life and fault codes: Generac support articles and owner’s manuals, read October 2026; Generac FAQ (6-month dealer service). Kohler (Rehlko) maintenance schedule and service pages, read October 2026. Maintenance cost: HomeAdvisor, 2026. Fuel stabilizer: STA-BIL maker data. Safety: CPSC 2026 and Ready.gov. Commercial rules: NFPA 110 overview (NFPA) and EPA stationary engine fact sheets; NFPA 110 test routine from industry summaries. Cancellation rights: FTC Cooling-Off Rule. Estimates on this page are ours and labelled.