Last verified: October 1, 2026
Short answer: your standby generator’s exercise timer starts the engine on a schedule so that problems show up before an outage, not during one. On Generac’s air-cooled models the exercise can be set to run weekly, every two weeks or monthly, on the day and at the time you choose, and each run lasts about 5 or 12 minutes depending on the model, at reduced engine speed. Weekly is the safest setting for most homes; the fuel it uses over a year is small compared with a single day of outage running.
What the exercise actually does
- Proves the generator starts: the battery has to crank the engine, the fuel has to flow and the controller has to manage the start.
- Keeps the engine healthy: it circulates oil, lubricates seals and moving parts and warms the engine to drive off moisture.
- Exercises the electronics: the controller logs the run and raises an alarm if something is wrong, while you still have utility power to fix it.
- Keeps the battery charged and tested.
During the exercise, the house normally stays on utility power. The generator runs by itself without taking over your loads, unless the utility fails during the test.
Generac’s exercise settings
| Setting | Options |
|---|---|
| Frequency | Weekly, biweekly or monthly |
| Day and time | The day of the week (or a day of the month, for monthly) and the time of day you choose |
| Duration | About 5 or 12 minutes, depending on the model |
| Engine speed | Reduced speed “Quiet-Test” mode on Guardian models |
| Required mode | The exercise only runs when the controller is in Auto |
Source: Generac owner’s manual for 60 Hz air-cooled generators (9–22 kW). Two details from the manual are easy to miss: the exercise timer does not adjust for Daylight Saving Time, and the timer and clock must be reset if the battery dies or is disconnected.
Choosing the best schedule
| Setting | Pros | Cons | Good for |
|---|---|---|---|
| Weekly | Catches problems fastest; keeps engine and battery in the best condition | Slightly more fuel and noise over a year | Most homes, especially in storm areas |
| Every two weeks | Half the weekly runs | A problem can go unnoticed for up to two weeks | Homes where noise is a sensitive issue |
| Monthly | Least fuel and noise | A dead battery or closed fuel valve can go unnoticed for weeks | Rarely the best choice for a home that relies on its generator |
How much fuel does it use?
Very little. A weekly test of 5–12 minutes adds up to roughly 4–10 hours of running a year, at low speed. Generac’s brochure describes Quiet-Test as consuming less fuel than a normal run. For comparison, a single day of outage running is 24 hours. It’s not worth reducing the exercise to save fuel.
When to schedule it
- Late morning on a weekday is usually considerate to neighbors.
- Pick a time when someone is often home, so the test is seen and heard occasionally.
- Avoid early mornings and weekend evenings if the unit is near bedrooms or patios.
What the exercise costs in fuel: an upper limit
Generac doesn’t publish fuel use for the low-speed exercise, but we can put a ceiling on it. The table below assumes, generously, that the generator burns as much during the test as a 22 kW unit at half load (221 cubic feet of natural gas or 2.53 gallons of propane per hour), using the same prices as our cost-vs-outage guide: $15 per 1,000 cubic feet of natural gas and $2.67 per gallon of propane. The real figure is lower, because the exercise runs at reduced speed without powering the house.
| Schedule | Running hours per year | Natural gas, upper limit | Propane, upper limit |
|---|---|---|---|
| Weekly, 12-minute exercise | About 10.4 | About $34 | About $70 (26 gallons) |
| Weekly, 5-minute exercise | About 4.3 | About $14 | About $29 (11 gallons) |
| Every two weeks, 12 minutes | About 5.2 | About $17 | About $35 (13 gallons) |
| Monthly, 12 minutes | 2.4 | About $8 | About $16 (6 gallons) |
Even at the ceiling, a full year of weekly exercises costs less than half of what one day of outage running costs at half load (about $80 on natural gas or $162 on propane). Switching from weekly to monthly saves a few dollars a year in exchange for finding a problem up to a month later, which is rarely a good trade.
If you are on propane, the exercise does use some of your tank. Twenty-five gallons or so a year is small compared with a 250- or 500-gallon tank, but it is one more reason to check the gauge before storm season rather than assuming the tank is still as full as it was at the last delivery.
The limit of the exercise: it doesn’t test the transfer
Because the weekly exercise normally runs without taking over your house loads, it proves the engine starts and runs, but not that the transfer switch works or that the generator can carry your appliances. Those are tested in a real outage, or when a technician runs a test under load. Two simple habits close the gap:
- Ask for a load test at the annual service. Ask the technician to confirm that the transfer switch moves the house to the generator and back, and that the unit carries your normal loads without alarms.
- Pay attention to the first hours of a real outage. Note how quickly the lights came back, whether the air conditioner or well pump started normally, and whether any alarm appeared. Tell your dealer about anything unusual at the next service.
Watch the exercise once a month
An exercise that runs unobserved can still hide problems. Once a month, be there when it runs:
- Listen: does it start promptly and run smoothly, without knocking or rattling?
- Look at the controller: any alarm or maintenance message? A Service A or Service B message means scheduled maintenance is due.
- Check that the vents are clear of leaves, snow, mulch and plants.
- On connected models, confirm the app records the exercise.
If the exercise didn’t happen, the most common reasons are that the controller isn’t in Auto, an alarm is active, or the clock was reset after a battery issue. See Generac Generator Alarms Explained and Generac Generator Won’t Start.
A simple exercise log
Keeping a one-line record each month takes seconds and gives your dealer useful information if a problem appears. A notebook kept near the indoor panel or a note on your phone is enough:
| Date | Started promptly? | Sound normal? | Controller status | Vents clear? | Notes |
|---|---|---|---|---|---|
| Example: first Tuesday of the month | Yes | Yes | Green, no alarms | Yes | Cleared leaves from the base |
After a power outage or battery change
Check the clock and exercise settings after any event that might have reset them: a battery replacement, a dead battery, or a dealer service where the battery was disconnected. Twice a year, when clocks change for Daylight Saving Time, check that the exercise still runs at the hour you want, because Generac’s timer does not adjust automatically.
What a healthy exercise looks like
| Sign | Healthy | Needs attention |
|---|---|---|
| Start | Starts within a few seconds | Long cranking, several attempts or an Overcrank alarm |
| Sound | Steady, even hum | Knocking, surging, rattling panels |
| Controller | Green status, no alarms | Red or yellow light, alarm message |
| Surroundings | No smell of gas, no oil on the ground | Gas odor (shut the fuel valve and call the utility), oil leaks |
Frequently asked questions
Can I turn the exercise off?
You shouldn’t. It is the generator’s main way of catching problems before you need it. If noise is the issue, change the schedule rather than disabling it.
Does the exercise power my house?
Normally not. The generator runs on its own while the house stays on utility power. If the utility fails during a test, the system transfers as it would in any outage.
Why did my generator exercise at the wrong time?
Most often because of Daylight Saving Time or a clock reset after the battery was disconnected. Reset the time and exercise schedule as described in your manual.
Bottom line
Keep the exercise on a weekly schedule, at a sensible time, and watch it once a month. Combined with the manufacturer’s service schedule in our maintenance checklist, it’s the simplest way to make sure the generator starts when the lights go out.