Most generator problems trace back to improper storage. Stale fuel, a discharged battery, and degraded oil account for the vast majority of "won't start" calls. A 30-minute prep session before putting your generator away will ensure it starts first pull when you actually need it — potentially months or years later.

Gas Generator Storage: Step-by-Step

Step 1: Decide on your fuel strategy

You have two options. Choose one and stick to it:

Option A: Fuel Stabilizer

  • Add fuel stabilizer to a full tank of fresh gas
  • Run the engine for 10 minutes to circulate through carburetor
  • Extends fuel shelf life to 12–24 months
  • Good for: generators stored 1–12 months between uses
  • Products: Sta-Bil 360, PRI-G, Star Tron

Option B: Run Dry

  • Close the fuel petcock (fuel shutoff valve)
  • Let the engine run until it stops from fuel starvation
  • Empties the carburetor completely — no varnish risk
  • Good for: generators stored 6+ months
  • Downside: must restart procedure from scratch with fresh fuel
⚠️ Do NOT store a generator with untreated regular gasoline in the tank for more than 30 days. Ethanol-blended fuel absorbs moisture and leaves varnish deposits in the carburetor that are expensive to clean. Either stabilize it or run it dry.

Step 2: Change the oil

If the oil is dark, dirty, or has been used for 25+ hours, change it before storage. Old oil contains combustion byproducts that are acidic — storing the engine in old oil accelerates internal corrosion. Fresh oil is cheap insurance. See our oil change guide →

Step 3: Fog the cylinder (for storage over 6 months)

Remove the spark plug and spray engine fogging oil into the cylinder while slowly pulling the recoil cord to coat the cylinder walls. This prevents rust formation during extended storage. Reinstall the spark plug (hand-tight, then 1/8 turn with wrench).

Step 4: Battery maintenance (electric start models)

For storage under 3 months: disconnect the battery negative terminal to prevent slow discharge. For storage over 3 months: remove the battery and connect to a maintenance charger (Battery Tender, NOCO Genius) that provides a trickle charge without overcharging. A dead battery is the most common reason an electric-start generator won't start after winter storage.

Step 5: Clean and cover

  • Wipe down all external surfaces with a clean cloth
  • Inspect air filter — clean or replace if dirty
  • Close all fuel valves and cap openings
  • Cover with a breathable generator cover (not plastic sheeting — moisture traps)
  • Store in a dry, ventilated location away from living spaces
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Storage Location Guidelines

  • Garage: Fine if dry and ventilated. Keep fuel containers away from the gas water heater, furnace, or any ignition source.
  • Shed: Good option. Ensure it doesn't flood in heavy rain and has some ventilation to prevent moisture buildup.
  • Outdoors: Acceptable with a proper breathable cover. Protect from direct rain exposure. Cold temperatures aren't harmful — generators handle winter storage well.
  • Indoors (living space): Gasoline storage indoors is a fire hazard. Generators should not be stored in living areas with attached garages being the accepted exception if ventilated.

Solar Battery Station Storage

Solar generators (battery power stations) are much simpler to store:

  • Store at 50–80% charge — not 100% (stresses LFP cells) and not 0% (risks over-discharge)
  • Check charge level every 3 months — top up if below 30%
  • Store at room temperature — avoid attics or sheds with temperature extremes above 95°F or below 14°F for extended periods
  • No fuel, no oil, no carburetor — just charge it periodically and it's always ready

Returning to Service After Storage

  1. If ran dry: add fresh fuel (ethanol-free if available), reconnect battery
  2. If stabilized: verify fuel is within 12 months — if older, drain and add fresh
  3. Check oil level — add if needed
  4. Inspect air filter — replace if not done before storage
  5. Check spark plug — clean gap or replace
  6. Start and run under load for 10–15 minutes — verify all outlets work
  7. Check for fuel, oil, or exhaust leaks during run

Frequently Asked Questions

How long can I store a generator?
With proper preparation — stabilized fuel or run dry, fresh oil, fogged cylinder for long-term storage — a generator can be stored for years without issues. Generators stored correctly in garages for 5–10 years typically start and run normally after proper return-to-service prep. The engine itself doesn't degrade from sitting — the fuel system and battery are the only storage-sensitive components.
Should I store my generator with a full or empty fuel tank?
Either — but not with untreated partial fuel. Full tank with stabilizer: prevents condensation inside the tank and inhibits fuel degradation. Empty tank (run dry): eliminates all fuel from the system. Both work. A partial tank of unstabilized fuel is the worst option — it degrades faster than a full tank and leaves the tank partially empty for condensation.
Can cold weather damage a stored generator?
Cold temperatures alone don't damage generators or engine components. What cold does affect: battery cold-cranking capacity (electric start may be weaker in very cold conditions), oil viscosity (use 5W-30 below 32°F for easier starting), and fuel — at temperatures below about -40°F, diesel and some gasoline formulations can gel, but this is not a concern in most of the US. Store in an unheated garage through winter without concern for the engine itself.

About the reviewer

Dale Harmon

Dale Harmon

Residential electrician - Charlotte, NC

Dale has 18 years of hands-on electrical work and started testing backup power equipment after Hurricane Florence left his neighborhood without power for nine days. Every product on this site is purchased at retail and run through structured load tests before he writes a word.

More about Dale and our testing process »