Winter is exactly when most standby generators earn their keep — and exactly when cold temperatures can cause problems if the unit hasn’t been prepared for them. Unlike a portable generator you store away, a standby unit stays outside year-round, so «winterizing» is less about storage and more about making sure it’s ready to perform reliably in the cold.
Why Cold Weather Affects Generator Performance
- Battery capacity drops in cold temperatures, which is part of why battery issues (already the most common no-start cause — see our guide to Generac not starting) become more frequent in winter specifically.
- Oil thickens in the cold, which is why using the correct seasonal oil weight matters more in winter than any other time of year.
- Propane vaporization slows down in extreme cold, which can affect fuel delivery for propane-powered units in particularly harsh climates.
Winterizing Checklist
1. Check the Battery Before Cold Weather Hits
Cold weather is the single biggest stress test for a weak battery. Have it load-tested (not just visually inspected) in early fall, before temperatures drop — a battery that’s marginal in October often fails outright in January.
2. Switch to Cold-Weather Oil if Recommended
Some manufacturers recommend a different oil viscosity for winter operation, especially in regions that see sustained sub-freezing temperatures. Check your model’s manual or ask your installer whether a seasonal oil change makes sense for your climate.
3. Install a Cold Weather Kit if You’re in an Extreme Climate
Many Generac and Kohler models offer an optional cold weather kit — typically a battery warmer and oil heater — for regions with consistently harsh winters. If you’re in the northern Midwest, upper New England, or similar climates, this is worth asking your installer about specifically, since it directly addresses the two biggest winter failure points (battery and oil).
4. Clear Snow and Ice Accumulation
Keep the area around the unit clear of snow buildup, and make sure the exhaust and intake areas specifically stay unobstructed — a blocked exhaust in particular is both a performance issue and a safety concern.
5. Confirm Propane Tank Access
If you’re on propane, make sure the tank and its regulator are accessible and not buried under snow drifts, since your delivery service and any technician will need clear access.
6. Run a Manual Test Before the First Major Storm
Even with the weekly automatic self-test running, it’s worth manually verifying full operation — including actually transferring load — once before winter’s first serious storm, rather than assuming the self-test alone guarantees full performance under real conditions.
Signs Your Generator Isn’t Winter-Ready
- The weekly self-test runs noticeably slower or louder than usual in cold weather
- Any hesitation or rough running during the self-test cycle
- A battery that’s more than 2-3 years old without a recent load test
- Visible ice buildup directly on or around the unit’s intake or exhaust
Frequently Asked Questions
Do I need a cold weather kit if I only get occasional light frost? Usually not — cold weather kits earn their cost mainly in climates with sustained, hard freezes, not areas with mild or occasional cold snaps.
Can extreme cold damage a generator that isn’t running? Generally no, standby generators are built to sit outside year-round, but a battery that was already weak going into winter is far more likely to fail completely in sustained cold than in mild weather.
Should I cover my generator during winter? Most manufacturers specifically advise against fully covering the unit, since it needs airflow even when idle — a purpose-built vented cover (if you use one at all) rather than a generic tarp is important if you choose to use one.
Bottom Line
Winterizing a standby generator mostly comes down to battery health, correct oil viscosity, and keeping the unit’s exhaust and intake clear — the goal isn’t storage prep, it’s making sure the system performs when winter storms are exactly when you’re most likely to need it.