How Long Should You Wait Before Starting Your Portable Generator?
Short answer
Wait 15 minutes as a general rule. Shorter outages are usually grid hiccups that resolve on their own — cranking up immediately wastes fuel and causes unnecessary engine wear.
The 15-minute rule
Utilities use automatic recloser switches that attempt to restore power within a few minutes. Starting your generator too early means you may be running it while the grid is already recovering.
Under 5 minLikely a temporary grid hiccup — wait it out.
5 – 15 minUtility recloser cycles in progress — prep the generator but hold off.
15 min+Usually a physical fault (downed line, blown transformer) — start up.
When to skip the wait
Three situations where you should start sooner:
- Extreme temperatures.If it's 95°F+ or below freezing, HVAC or heat becomes a safety issue. Start within 5 minutes.
- Critical loads. Medical equipment, oxygen concentrators, or a sump pump during active flooding — start immediately.
- Fuel type. Propane and natural gas generators have minimal cold-start wear, so starting earlier is lower risk. Gasoline generators benefit from the wait to avoid unnecessary carburetor strain.
How to know when grid power is back
With an interlock or transfer switch installed, your home is isolated from the grid — you can't just look at a light to know if utility power returned. Three reliable methods:
- Sacrificial light. Leave one circuit (e.g., porch light) off the transfer switch. When it turns on by itself, the grid is back.
- Grid power alarm. A device like the Reliance Controls THP108 monitors your main panel and alerts you audibly when utility power restores.
- Smart plug on a grid-only circuit. When it reconnects to Wi-Fi, your phone gets a notification automatically.
Summary
| Outage duration | Action |
|---|---|
| 0 – 10 min | Wait. Check your utility's outage app. |
| 10 – 15 min | Prep the generator — move it to the pad, check oil and fuel. |
| 15 min+ | Start it up and flip the interlock. |