After the storm: what to do with your generator once the power is back

The power is back. The generator has done its job — or it has not, and you need to know which. This page is what to do in the days after a storm: how to shut the generator down properly, what to check before the next outage, and the fuel maths that decides whether the unit was ready in the first place.

The short answer

When the power returns, let the generator run for a few minutes to cool down, then shut it down — either by switching the transfer switch back to utility power and letting the generator cool and stop, or by switching the generator to off after the transfer switch has moved the load back. Then check three things: the oil, the fuel, and the fault log. A generator that ran for days needs an oil check and a service visit. A generator that faulted needs a technician before the next storm.

Figures last reviewed November 2026 · Sources: manufacturer service guidance (Generac, Kohler); Palm Beach County installed-cost research — see “How we get our numbers” on the About page.

The 24-hour rule: why a generator needs a rest

A standby generator is built to run for days. But it is not built to run indefinitely without a pause. Generac’s guidance is specific: after 24 hours of continuous running, shut the generator down for 30 minutes — to let it cool, to check the oil, and to let the engine rest. Then restart it. The 30-minute shutdown is not a suggestion. It is the point at which the oil is checked and topped up if needed, and the engine is given a chance to shed heat. A generator that runs for three days without a pause is a generator that is being asked to do something its manufacturer did not design it to do.

In practice, the 24-hour rule is the owner’s responsibility, not the generator’s. The generator will keep running. Somebody has to decide to shut it down for half an hour — and somebody has to remember to start it again. If the house is empty, that somebody is the property manager, the neighbour, or the monitoring app’s alert. This is one more reason the monitoring matters: the app shows how long the generator has been running, and the 24-hour mark is visible on the phone of whoever is watching.

What to check once the power is back

Do this in the day or two after the power returns, while the storm is still fresh and before the next one:

• Oil level. Check it. A generator that ran for days has consumed oil. If the level is low, top it up — with the oil the manufacturer specifies, not whatever is in the garage. If the generator ran for more than 24 hours, the oil change interval may have been reached. Check the manual, and book a service visit if it has.
• Fault log. Open the monitoring app, or read the controller’s display. Is there a fault logged — overcrank, low oil, overspeed, undervoltage? A fault that appeared during the storm is a fault that needs a technician before the next storm.
• Exercise. Confirm the generator is back in automatic mode, and that its weekly exercise is still scheduled. A generator that was switched to manual during the storm — to shut it down for the 30-minute rest, for instance — needs to be switched back. A generator left in manual is a generator that will not start next time.
• Fuel. Propane: check the tank level. A long run can take a tank down further than you expect, and the next storm does not wait for a delivery. Natural gas: there is nothing to check — the supply is the utility’s — but confirm the shutoff valve is open and the connection is sound.
• The house. Walk the rooms. Is the air conditioning running? Is the refrigerator cold? Any smell of damp, any stain on a ceiling? The generator’s job was to keep the house powered. The walk-through confirms it did.

The fuel maths: how long a tank actually lasts

A propane tank does not last as long as people think. The arithmetic:

• A 250-gallon tank, filled to the usual 80%, holds about 200 gallons of usable propane.
• A 22 kW generator at half load burns about 2.5 gallons an hour. At that rate, 200 gallons lasts about 80 hours — a little over three days.
• At full load, the same generator burns about 3.9 gallons an hour. At that rate, 200 gallons lasts about 51 hours — a little over two days.
• A 500-gallon tank, filled to 80%, holds about 400 gallons — roughly double those figures.

What this means in practice: a 250-gallon tank is enough for a typical storm outage, if the generator is not carrying a full load the whole time. It is not enough for a week-long outage at full load. If the house is on propane, the tank size is a decision to make before the season, not during it — and the propane vs. natural gas page covers the sizing in full.

When to call a technician

Call a technician — not next month, this week — if any of these is true:

• The generator faulted during the storm, and the fault is still logged.
• The generator ran for more than 24 hours, and the oil has not been checked since.
• The generator sounds different from before the storm — a new noise, a rougher start, a vibration that was not there.
• The generator did not start at all, and the power was out. That is the failure the fail-to-start page is about — and it needs a diagnosis, not a hope.
• The transfer switch did not transfer, or transferred late, or the house was dark while the generator was running.

The week after a storm is the busiest week of the year for generator technicians. Plan customers are answered first. One-off callers wait. If you are on a service plan, call the plan’s number. If you are not, call now — and consider whether the plan is worth it before the next season. The service plan page explains what a plan covers.

Related: Maintenance & service plans · Propane or natural gas: which fuel should your standby generator use? · Remote monitoring

Palm Beach Backup Power is an information and matching service — we do not install generators. We do not take a fee from you. Our installer partner pays us when a consultation they receive through us becomes an installed generator. The price you pay is the installer’s price either way.