A generator that sat in the garage all year is only useful if it starts when the power goes out. The short answer: run a regular test per your owner’s manual, add fuel stabilizer to any gasoline you store, keep the unit and its fuel away from living spaces, and inspect cords and the carbon monoxide (CO) alarm before you ever need any of it. This guide walks through what to check, how often, and why skipping it is dangerous.
Warning Signs First: When a Stored Generator Is Not Safe to Use
Do not start or run a generator if you see any of these. Stop and inspect or repair before use.
- Fuel smell inside the house or garage — this means a leak or improperly stored fuel. Fix before doing anything else.
- Cracked, brittle, or exposed wiring on cords or the generator’s own power cable.
- Rust, corrosion, or oil leaking from the fuel tank or engine housing.
- Gasoline stored longer than the stabilizer’s rated shelf life without treatment — old gas can gum up the carburetor and won’t burn cleanly.
- No working carbon monoxide alarm in the home. The Consumer Product Safety Commission (CPSC) recorded about 750 generator-related CO deaths in the United States between 2012 and 2022, and says CO from a running generator can reach deadly levels indoors within minutes.
Never Run a Generator Indoors — Even “Just for a Minute”
This rule does not change for testing, maintenance, or bad weather. Per CPSC, portable generators must run outdoors only, at least 20 feet from the home, with the exhaust pointed away from windows, doors, and vents. Never run one in a garage, basement, shed, or crawlspace, even with the door open. Carbon monoxide is invisible and has no smell, and it can build up before you notice anything is wrong.
Install CO alarms that meet UL 2034, IAS 6-96, or CSA 6.19.01 standards, and test the batteries monthly, per CPSC guidance.
Fuel Storage and Stabilizer: The Part Most People Skip
Gasoline breaks down over time. The U.S. Department of Energy’s Building America Solution Center notes that fuel stored for backup power may need a stabilizer added to the tank to prevent spoilage, and that households should keep a regular testing schedule for both the generator and the fuel storage setup.
- Add fuel stabilizer to gasoline you plan to store for more than a month or two, and follow the product label for the correct ratio and re-treatment interval.
- Store fuel outside living areas, in approved, properly labeled, non-glass safety containers — never in the house, and away from any fuel-burning appliance such as a gas water heater, per CPSC.
- Keep the area around the generator clear of weeds, dry grass, and debris, since these are combustion hazards, per DOE’s Building America guidance.
- Rotate old fuel into your vehicle or lawn equipment before it ages past the stabilizer’s rated window, then refill with fresh fuel and stabilizer.
For a full breakdown of safe storage limits and containers for gasoline, propane, and kerosene, see our emergency fuel storage safety guide.
Maintenance Checklist: What to Check and How Often
- Start-and-run test, outdoors, 20+ feet from the home, under a small load — do this per your owner’s manual’s recommended interval. It confirms the engine starts and the electrical output works before an emergency, not during one.
- Check oil level and condition — before every test run and before putting the generator into storage. Low or dirty oil can damage the engine on startup.
- Inspect fuel for age and add stabilizer — every time you refill stored fuel, or per the stabilizer’s label. Stale fuel can clog the carburetor and prevent starting.
- Inspect cords, plugs, and connections — before every use. Damaged cords are a shock and fire risk.
- Test CO alarm batteries — monthly, per CPSC guidance. It’s your only warning against an invisible, odorless gas.
- Clear debris and dry vegetation around the storage area — seasonally, to reduce fire risk from stored fuel and combustion sources.
If you have not sized your generator against your actual appliance load, our generator sizing and transfer switch guide walks through the running-watts and starting-watts math before you buy or upgrade.
Startup Checklist Before an Emergency
- Move the generator outdoors, at least 20 feet from the home, exhaust facing away from windows and doors.
- Check oil level and top off if needed.
- Check fuel — if it’s old and untreated, drain it and refill with fresh, stabilized fuel.
- Inspect the power cord and any extension cords for cracks, exposed wire, or damaged plugs. Use only heavy-duty, outdoor-rated extension cords sized for the connected load, per CPSC.
- Never refuel while the generator is running. Turn it off and let it cool first, per CPSC.
- Confirm your CO alarms are installed and working before you rely on the generator overnight or for extended periods.
Which Generator Type Should You Buy or Maintain This Way?
This guide covers upkeep once you already own a generator. If you’re still deciding between a portable conventional generator, a portable inverter generator, or a standby system, see our emergency generator comparison for output capacity, noise, runtime, and cost differences. For the first hours after the power goes out, our power outage first-24-hours checklist covers immediate safety steps beyond the generator itself.
Extra Caution: Homes and Households That Need More Margin
Some situations call for extra care and less room for error:
- Anyone using electricity-dependent medical equipment should have a plan that does not rely on a generator starting on the first try — talk with the equipment supplier about backup options.
- Attached garages are not a safe generator location even with the door open. CO can still migrate into the home.
- Households with older adults, infants, or anyone who cannot easily evacuate quickly should test CO alarms more often and confirm everyone in the home knows the alarm sound.
- Apartments, condos, and homes without 20 feet of clearance from the structure may not have a safe location for a fuel-burning generator at all — a battery-based backup power option may be a safer fit.
Frequently Asked Questions
How long can I store gasoline for my generator?
Untreated gasoline degrades over time and can cause starting problems. Adding a fuel stabilizer extends usable shelf life — follow the specific product’s label for its rated storage window and re-treatment schedule, since this varies by brand and formulation.
How often should I start and run my generator to keep it ready?
Follow your specific generator’s owner’s manual for the recommended test-run interval and procedure. Always run the test outdoors, at least 20 feet from the home, per CPSC guidance.
Can I store my generator in the garage?
Storing it there when it’s off and disconnected is common, but you must never run it in the garage, even with the door open. Move it fully outdoors, at least 20 feet from the home, before starting it, per CPSC.
Do I need a carbon monoxide alarm if I only run the generator outside?
Yes. CO can still migrate indoors through windows, doors, and vents even when the generator is outdoors. CPSC recommends installing CO alarms that meet UL 2034, IAS 6-96, or CSA 6.19.01 standards and testing them monthly.
Educational Disclaimer
This article is for general educational purposes and is not a substitute for your generator’s owner’s manual, a licensed electrician, or guidance from the Consumer Product Safety Commission or the U.S. Department of Energy. Follow your manufacturer’s specific maintenance and safety instructions, and consult a qualified professional for installation, wiring, or repair work.