Key Takeaways
- Follow safety, maintenance and use instructions in our article and your manual.
- Generator run times vary by generator efficiency, device power requirements, fuel tank size and more.
- A 7,500-running-watt gasoline generator at 50-percent load can use 1/2 to 3/4 of a gallon of gasoline per hour.
- A 6,750-running-watt propane generator at 50-percent load can use 2 to 3 pounds of propane per hour.
- Compare starting and running wattages for the devices you need to run to the generator specifications.
- Store fuel according to fire codes, in a secure detached shed or detached garage and away from the sun, heat and ignition sources.
- Gasoline with stabilizer can last one to two years and while propane has no expiration date, you might need to replace the propane tanks.
- This article contains safety warnings and callouts — please read the entire article.
What to Know Before Using a Generator
Before you start preparing for an outage, get familiar with generator safety and be aware of some terms that will help you plan.
Safety Tips for Using a Generator
Follow all safety precautions in your manual, but keep this information in mind:
- The exhaust from portable generators contains carbon monoxide (CO), a deadly, poisonous gas you can’t see or smell.
- Don’t run a generator indoors or in an enclosed space, such as a garage, shed or crawlspace.
- Operate a generator at least 20 feet from the home, with 3 to 5 feet of clearance on all sides and the exhaust pointed away from the home.
- Don’t refuel a hot generator.
- Don’t run a generator exposed to rain or snow or in a wet location.
- Don’t touch a generator with wet hands.
- Don’t connect a generator to a home electrical outlet.
- Don’t connect a generator to a home power system except by means of a transfer switch installed by a licensed electrician.
- Don’t connect multiple extension cords together.
- Use heavy-duty grounded outdoor extension cords rated for the power your devices draw.
Generator Fuel Consumption and Runtimes
This guide offers estimates for portable generator fuel consumption and runtimes, as well as examples of what you can run on the generator. Use this information for general planning only. Use your generator documentation and the actual power requirements for your devices to estimate capacity, runtimes and fuel needs.
Keep these terms in mind:
- Load: Electrical power devices draw from the generator.
- Device: Any appliance or electric item.
- Running Watts: The amount of power a device uses during normal operation.
- Starting Watts: The greater amount of power some devices use when starting.
- Generator Capacity: The starting and running wattage a generator can provide.
Our generator storm outage checklist gives you tips on portable generator prep, use and maintenance.
Estimating Generator Runtime
Generator runtime depends primarily on several factors, including:
- Fuel tank size
- Amount of fuel in the tank
- Generator efficiency
- Starting and running wattages of the connected devices
How Long Does a Generator Run on Gas or Propane?
The actual generator run time varies widely depending on the factors above, and wattage capacities vary, but as general estimates:
- A 7,500-running-watt gasoline-powered generator at 50-percent load might use between about 1/2 and 3/4 of a gallon of gasoline per hour.
- A 6,750-running-watt propane-powered generator at 50-percent load might use between about 2 and 3 pounds of propane per hour.
These are broad ranges. Your documentation should tell you the actual fuel consumption rate for your generator.
Keep these factors in mind:
- A dual-fuel generator that creates 7,500 running watts with gasoline might create only 6,750 running watts on liquid propane (LP), since gasoline provides more energy.
- A filled 20-pound propane tank typically contains between 17 and 18 pounds of liquid propane, to allow for expansion.
Inverter generators, which throttle up or down depending on the actual electrical load (for example, as a refrigerator switches on and off) will be more efficient, potentially giving you more runtime.
What Can You Run on a Generator at 50-Percent Load?
What you can run on a generator at the same time depends on the generator’s capacity and the power usage of the devices. However, using a dual-fuel generator that produces 7,500 running watts and 9,400 starting watts with gasoline, and estimating usage for some typical devices, you could power these items at the same time:
- Refrigerator (700 watts)
- Chest freezer (600 watts)
- Microwave (1,100 watts)
- Box fan (200 watts)
- Two phone chargers (20 watts)
- Modem and router (20 watts)
- Laptop (60 watts)
- LED television (150 watts)
- Eight 10-watt LED light bulbs (80 watts)
If running the generator on propane supplies 6,750 running watts and 8,540 starting watts, you could power similar items, but you need to swap some of your non-essentials in and out of rotation. You could run items like these at the same time:
- Refrigerator (700 watts)
- Chest freezer (600 watts)
- Microwave (1,100 watts)
- Two phone chargers (20 watts)
- Modem and router (20 watts)
- LED television (150 watts)
- Eight 10-watt LED light bulbs (80 watts)
Both examples keep power requirements comfortably below the 50-percent load point. Starting wattages for the appliances and fan exceed the 50-percent load estimate briefly but should be within the capabilities of the example generator. Check product information for your specific devices to collect starting and running wattages and compare them to your generator capacity.
Don’t have a generator? Read our generator guide to learn about your options. Use our Wattage Calculator to estimate running watts of your devices and find recommended generators.
Using the Generator Over a Long Outage
If the outage lasts several days and you need different devices, like a range or coffee maker, you can keep the refrigerator and freezer running and swap out non-essentials.
How Often to Refuel a Generator
Use fuel consumption estimates to plan for refueling — be conservative. You shouldn’t let a generator run out of fuel while it’s powering devices. So, if you have a generator with a full 8-gallon gas tank and it uses a little more than half a gallon every hour, you might want to refuel after 10 hours. Be sure to follow the manufacturer’s instructions for shutting down, refueling and restarting the generator.
Generator Fuel Storage and Safety
Use your generator’s consumption rate to plan a good supply of fuel for an outage. Follow the safe storage practices and fire codes for your area, but consider these tips:
- Store fuel only in approved containers that are in good condition.
- Store fuel outside of the home, such as in a ventilated, detached shed or detached garage.
- Keep fuel away from direct sun, heat sources and sparks.
- Keep children and pets away from the storage area.
- Fire codes often specify storing gasoline in containers with capacities of 5 gallons or less, for a maximum of 25 gallons total.
- Fire codes often specify storing a maximum of 100 pounds of propane.
- Make sure the valves on propane tanks are fully closed.
How Long Gas Lasts in Storage
Purchase only the amount of pump gasoline you can use in 30 days or treat the gasoline with a fuel stabilizer. A fuel stabilizer can keep gasoline usable for up to one or two years, depending on the product.
How Long Propane Lasts in Storage
Propane doesn’t degrade and doesn’t have an expiration date. However, propane tanks do need to be replaced or inspected and requalified 12 years after the manufacture date stamped into the tank collar. Suppliers won’t refill an out-of-date tank.
Keep Your Generator Running and Your Lights On
Knowing your generator can run for the duration of an outage helps you keep the lights on and critical devices running. Shop Lowes.com for a generator size to fit your needs and find the extension cords and other accessories you need. If you have questions, stop by your local Lowe’s and talk to one of our Red Vest associates. They’ll help you find the right generator and accessories so you’re ready for any storm or power outage.
Generator Runtime and Fuel FAQ
Use the answers to these questions to make sure your generator is ready for an outage and can keep your critical devices running.
How Long Can a Generator Run Before It Needs to Be Powered Down?
Check your manual for specific run and rest times, but typically you can run a generator for eight to 12 hours, or until it needs refueling, whichever comes first. However, there might be maintenance steps, such as adding or changing the oil and changing the air filter, that might require shutting down a generator.
What Can a 5000-Watt Generator Run?
A 5000-Watt generator can power a couple of essentials and a few other examples, provided it has enough starting-watt capacity. For example, using some broad estimates it could power these items at the same time:
- Refrigerator (700 watts)
- Eight 10-watt LED bulbs (80 watts)
- Well pump (1000 watts)
- Television (150 watts)
- Two phone chargers (20 watts)
These running wattages would use less than 50 percent of the generator capacity. Starting watts for the refrigerator and pump could bring the total to 5,350 watts, so make sure the starting watt capacity of the generator is sufficient. Always check the actual running and starting wattages of your devices so you don’t overload the generator.
What’s the Difference Between Running Watts and Starting Watts?
Running watts indicate the amount of power an electric device uses during normal use. Starting watts for a device indicate the power necessary for a device with a motor, such as the motor on a refrigerator compressor or a fan motor, to start. Starting watts can be two to three times higher than running watts.
Can You Run a Generator in the Rain?
Manufacturers specify you shouldn’t run a generator in the rain, unless it’s protected by a manufacturer-approved in-use or running cover. If you don’t have an in-use cover, keep the generator in storage. When you do run the generator, be sure to keep it clear of any puddles or standing water.