Generator Maintenance Checklist: Keep Your Backup Ready

Why Maintenance Matters

A generator is an emergency tool that sits idle most of the year — and that is exactly why it needs a routine. Engines that aren't run regularly develop sticky carburetors, dead batteries, and stale fuel. The worst time to discover a problem is during a storm, when every hardware store is sold out of parts and every technician is booked. A simple maintenance routine takes a few hours a year and is the difference between a generator that starts on the first pull and one that fails exactly when you need it. This checklist covers monthly, quarterly, and annual tasks for both portable and standby generators.

Monthly Checks (About 10 Minutes)

• Run the generator under load. Exercise the unit for 20 to 30 minutes once a month. For standby units, the automatic weekly self-test handles this, but verify it actually ran. Running keeps seals lubricated, burns off moisture inside the engine, and keeps the battery charged.
• Check the battery. Inspect the terminals for corrosion and clean them with a wire brush if needed. A healthy, fully charged battery reads around 12.6 volts or higher with the engine off. Standby generators have a built-in charger, but portable units need a trickle charger or a monthly run to stay topped up.
• Inspect for pests and debris. Mice love warm engines and chew wiring; wasps love exhaust ports. Open the enclosure and look for nests, droppings, and chewed wires, and clear leaves, grass, and snow away from the air intake and exhaust.
• Check fuel level and condition. For gasoline units, confirm the tank is full and treated with stabilizer. For propane, check the tank level. If you smell fuel or see oily residue or hissing near the lines, shut down and call a professional.

Quarterly Tasks (30 to 60 Minutes)

• Change or check the oil. Most air-cooled generator engines call for an oil change every 50 to 100 hours of run time — or at least once a year, whichever comes first. Check the oil level before every run, and keep the manufacturer's recommended oil type on hand; many newer units use synthetic 5W-30 or 10W-30.
• Clean or replace the air filter. A clogged filter chokes the engine, wastes fuel, and causes hard starting. Foam filters can be washed and re-oiled; paper filters get replaced. Check it every season, and more often in dusty conditions.
• Inspect the spark plug. Remove it, check the gap, and look for heavy carbon buildup or oil fouling. Replace it annually or every 100 hours — a fresh plug is cheap insurance for reliable starts.
• Test with a real load. Plug in space heaters, a hair dryer, or a load bank to pull at least half of the generator's rated wattage for 30 to 60 minutes. Light loads don't stress the engine enough to reveal problems; a solid load test confirms the unit handles both surge and sustained output. This is the single most valuable test you can run.

Annual Service

Once a year — ideally before storm season — do a full service, or pay a professional to do it:

• Oil and filter change, air filter service, and spark plug replacement.
• Valve clearance check on many air-cooled engines (a dealer service item).
• Coolant check on liquid-cooled standby units.
• Battery load test, and replacement if the battery is more than 3 to 5 years old.
• Transfer switch exercise: for standby systems, cycle through a simulated outage to confirm the switch works.
• Exhaust system inspection for rust, holes, or leaks — carbon monoxide safety depends on it.

For standby units, an annual dealer visit is worth the cost: technicians check things homeowners can't, and the service record keeps your warranty valid.

Fuel and Battery Care

• Gasoline: Use fresh fuel and add fuel stabilizer. Untreated gasoline degrades in as little as 30 to 90 days; stabilized fuel can last a year or more. If the generator will sit for more than a few months, drain the carburetor bowl or run the engine dry to prevent gummed-up carburetors — the most common cause of "won't start."
• Propane: Propane stores indefinitely, but check the tank level, valves, and hoses for leaks annually, and know your tank's capacity so you can estimate runtime.
• Natural gas: Nothing to store, but have the line and connections inspected during annual service.
• Batteries: Keep terminals clean and lightly coated with dielectric grease. Keep portable-unit batteries on a smart charger or maintainer, and confirm the standby unit's built-in charger is working.

Before and After Every Storm

Before: Top off the fuel, check the oil, run a 10-minute test, and confirm you have extension cords, a working carbon monoxide alarm, and fresh batteries. Clear the area around the generator.

After: Let the generator cool, then check oil and fuel, clean debris from the enclosure, and note any issues in your maintenance log. If you ran the unit hard for days, schedule an oil change before the next outage.

Common Problems and Quick Fixes

• Won't start: Check fuel freshness, battery charge, and spark plug. Stale fuel and dead batteries cause the majority of failures.
• Runs rough or surges: Usually a carburetor or fuel issue — clean or replace the carburetor, or check for water in the fuel.
• Low output: Could be a tripped breaker, a failing voltage regulator, or an overloaded generator. Test with a known load and a multimeter.
• Oil leaks: Check the drain plug, filter, and seals, and fix leaks promptly — don't just top off the oil.

Keep a Maintenance Log

Write down every service: date, hours on the meter, oil changes, filter replacements, and test results. A log reminds you when service is due and gives a technician — and your warranty claim — a clear history. Most generators have an hour meter; use it. If you prefer digital, a simple spreadsheet works fine.

The Bottom Line

An hour of maintenance a quarter is a small price for a generator that starts when the lights go out. Follow this checklist, keep your fuel fresh and your battery charged, run the unit under load regularly, and your backup will be ready for whatever the grid throws at you. For exact service intervals and specifications for your specific model, check the owner's manual or look the unit up on GeneratorDatabase (generatorsdatabase.com).