How to Store a Generator Long-Term

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The generator you bought for hurricane season three years ago and haven’t touched since is a maintenance time bomb. Old fuel gums up the carburetor, moisture corrodes electrical connections, the battery is dead, and when the next storm hits you’ll spend three hours cursing at the pull cord instead of running your fridge. Long-term generator storage isn’t complicated — it’s just a specific set of steps that most owners skip. Skip them and the generator becomes a paperweight; do them and it fires up the moment you need it, months or years later.

This guide walks through the correct process for storing a generator long-term: fuel handling, engine prep, battery care, physical storage conditions, and the periodic checks that keep the unit ready.

Why generators fail in storage

Common failure modes when generators sit unused:

Stale fuel: gasoline degrades in 30-90 days; ethanol-blended fuel worse. Varnish and gum deposits clog carburetor jets.
Corrosion in fuel system: ethanol attracts moisture; water separates in tank; corrodes aluminum carburetor and tank internals.
Dead battery (electric-start models): batteries self-discharge; deep-discharged batteries often can’t be recovered.
Rodent damage: mice chew wiring, nest in exhaust, block air intakes.
Corrosion on electrical connections: humidity causes oxidation on outlets, connectors, spark plug boots.
Rubber degradation: fuel lines, gaskets, and hoses harden and crack over years.
Rust on internal engine parts: condensation inside cylinders during temperature swings.

The good news: all of these are preventable with proper storage prep.

Long-term vs seasonal storage

Short-term storage (2-6 months)

Basic prep: run stabilizer through fuel system, top off tank, disconnect battery. Ready for next season with minor prep before use.

Seasonal storage (6-12 months)

All short-term prep PLUS fog engine, remove battery, cover unit, elevated storage. See our how to winterize a generator for the seasonal version.

Long-term storage (1+ years)

All seasonal prep PLUS drain fuel system entirely, remove/store battery separately, controlled environment storage, quarterly checks. This guide focuses on this scenario.

Step-by-step long-term storage prep

Step 1: Run stabilized fuel through the system (or drain entirely)

Option A: Stabilized fuel storage (up to 12 months)

Add a fuel stabilizer to the tank (Sta-Bil, Sea Foam, or Sta-Bil 360 Marine for ethanol-blend gas). Use per-manufacturer ratio.
Run the generator for 15-20 minutes so stabilized fuel reaches the carburetor and injectors.
Top off the tank completely — less air space = less moisture ingress.

Option B: Full drain (12+ months storage)

Run the generator until the tank is empty and it stalls.
Drain any remaining fuel from the fuel line and carburetor bowl (drain screw at bottom of carb).
For fuel-injected models: consult manufacturer for fuel line drain procedure.
Leave fuel cap slightly loose during storage to prevent vacuum buildup.

Rule of thumb: store empty for 1+ year; store with stabilizer for shorter periods.

Step 2: Change the oil

Old oil is acidic and corrodes engine internals during long storage. Fresh oil before storage protects the engine.

Run engine 5 minutes to warm oil (drains faster and completely)
Drain oil
Replace oil filter (if equipped)
Fill with fresh oil to specified level
Run 30 seconds to circulate fresh oil

Step 3: Fog the engine

Engine fogging spray coats internal engine surfaces with anti-corrosion oil, preventing rust on cylinder walls during storage.

Remove spark plug(s)
Spray fogging oil into cylinder for 3-5 seconds
Pull recoil (or crank without starting) 5-6 times to distribute oil on cylinder walls
Replace spark plug loosely (or leave out for extra-long storage)

Popular fogging oils: Sta-Bil Fogging Oil, Sea Foam, CRC Marine Fogging Oil.

Step 4: Battery removal and separate storage (electric-start models)

Batteries left connected to generators self-discharge in weeks and often can’t be recovered.

Disconnect negative terminal first, then positive
Remove battery from generator
Store on a wooden shelf or on a battery tender (float charger) in a cool, dry location
Check monthly if on tender; charge to full every 3 months if not on tender

Popular options: Battery Tender Jr 12V float charger — plug-and-forget for long-term battery maintenance.

Step 5: Clean the exterior

Wipe down exterior with mild detergent + water
Clean cooling fins with compressed air (dust reduces cooling efficiency)
Wipe electrical outlets/connections; spray with electrical contact cleaner
Check air filter — replace if dirty; clean if serviceable

Step 6: Protect from rodents

Mice love nesting in warm, sheltered generators.

Stuff steel wool into the exhaust outlet (remove before starting!)
Cover air intake with breathable fabric or fine mesh
Consider peppermint oil packets in the storage area (proven deterrent)
Traps in the storage area as backup

Step 7: Cover the generator

Use a proper generator cover — not a plastic tarp (which traps moisture).

Heavy-duty generator storage covers — breathable, waterproof, UV-resistant
Manufacturer-specific covers for whole-house standby units
Custom-sized covers for portable units

Step 8: Choose storage location

Ideal storage:

Dry (below 60% relative humidity)
Temperature-stable (40-80°F ideal; avoid extreme temperature swings)
Clean, dust-controlled space
Off the ground (pallet, shelf, cinder blocks)
Away from chemicals, fertilizers, pool chemicals (corrosive fumes)

Acceptable: garage, shed, basement (if dry), storage unit.

Avoid: uncovered outdoor storage, damp basements, areas near acidic chemicals.

Periodic checks during long-term storage

Monthly

Visual inspection: no leaks, no rodent damage, cover intact
Check battery voltage if not on tender

Quarterly (every 3 months)

Battery: charge to full if not on tender
Rotate/relocate cover if creasing to prevent permanent damage
Check for signs of rodent activity around unit
Verify storage area conditions unchanged

Every 6-12 months

Optional: run the generator for 15-20 minutes under light load to circulate oil and keep internals functioning (requires refueling with fresh gas + stabilizer, then re-storage prep)
Inspect fuel system for signs of degradation

Annually

Deep inspection: pull cover, inspect wiring, check for corrosion
Consider oil change even if not used (oil oxidizes over time)
Test any manual controls (choke, throttle)

Bringing a stored generator back into service

Pre-start checklist

Remove cover completely
Remove steel wool from exhaust (if used for rodent protection)
Inspect for damage, leaks, corrosion, rodent nests
Reinstall battery (electric-start models); charge if needed
Add fresh fuel with stabilizer
Check oil level (top off if needed)
Check air filter (clean or replace if dirty)
Verify spark plug is properly tightened
Wipe any moisture from electrical outlets and connections

Initial start attempt

Move to outdoor location with proper ventilation
Set fuel valve on, choke as needed
Attempt start — may need 3-5 pulls after long storage
If no start: check fuel supply, spark plug, and consult troubleshooting

Post-start warm-up

Let engine run 5-10 minutes at no load to warm up
Test all outlets with a small load (lamp, phone charger)
Listen for unusual sounds (indicates issues)
Check for oil or fuel leaks

If problems: refer to generator won’t start troubleshooting.

Common long-term storage mistakes

Leaving fuel in without stabilizer for 6+ months. Guaranteed carb problems. Either use stabilizer or drain empty.
Leaving battery connected. Discharges in weeks; often unrecoverable after months.
Using a plastic tarp as cover. Traps condensation; causes rust worse than uncovered.
Storing outdoors uncovered. UV degrades plastic; rain gets into fuel tank and electrical outlets.
Storing in wet basement. Constant moisture ruins electrical connections and engine internals.
Ignoring rodent protection. A single mouse can wire-chew a generator into unusability in weeks.
Not running the generator periodically. Occasional operation keeps seals and internals functioning; extreme long-term storage benefits from a run every 6-12 months.
Forgetting to remove steel wool from exhaust before starting. Engine damage if you forget this step.

Fuel storage separately

If you’re storing fuel supply alongside the generator (typical for hurricane season prep):

Gasoline: 5-gallon steel or approved plastic containers with proper venting
Stabilizer: add on fill-up, not later; extends shelf life to 12 months
Rotate: use stored gasoline in your vehicles at 6-month intervals
Propane: no shelf life issues; propane doesn’t degrade. Store per NFPA setback rules.
Diesel: 12-24 months with additives; treat with biocide to prevent bacterial contamination

See our fuel storage safety guide from OutageOutpost for the detailed fuel storage rules.

Recommended long-term storage supplies

Sta-Bil Fuel Stabilizer (32oz) — essential for any storage over 2 months
Sta-Bil Fogging Oil — internal engine protection during storage
Battery Tender Jr — keep batteries alive during long storage
Heavy-duty weatherproof generator cover — breathable, UV-resistant
Peppermint oil rodent repellent packets — mice don’t like the smell
Approved 5-gallon fuel cans — for backup fuel storage

Key takeaways

Long-term storage (1+ year): drain fuel, change oil, fog engine, remove battery, cover unit, controlled environment.
Fuel stabilizer good for 6-12 months; drain empty for longer storage.
Battery disconnected + on tender or charged quarterly is the difference between working and dead.
Rodent protection: steel wool in exhaust, breathable air intake cover, peppermint oil.
Periodic operation every 6-12 months keeps a stored generator ready — even if it’s just a 20-minute run.

FAQ

Should I drain the fuel or use stabilizer for a hurricane-season generator I only use once every few years? For irregular multi-year gaps, drain empty is safer. Even stabilized fuel becomes questionable after 12+ months. Drain fully, store empty, and refill with fresh fuel + stabilizer only when a storm is forecast. This is the approach used by military and emergency-service generator fleets.

Can I store my generator inside my house or attached garage? Attached garage yes — good temperature stability and dry conditions. Inside the house also acceptable if space allows (basement, utility room), as long as fuel is drained and the space is dry. Never store a generator in a bedroom or main living area with fuel present.

How do I know if long-stored gasoline is still usable? Fresh gasoline smells sharp and pungent. Stale gasoline smells sour, varnish-like, or musty. Visual: fresh is clear to light amber; stale becomes darker, sometimes with visible sediment. When in doubt, drain and refill with fresh. Bad fuel damages the carburetor faster than replacing it costs.