Generator Buying Guide

Performance
To test generators for performance, our expert engineers load up each model with a variety of essentials you might want to power during an outage, like a space heater, refrigerator, or window air conditioner. We make sure the generator can handle the load it promises and also determine what happens when a sudden spike in voltage hits, like what would happen if the compressor in your refrigerator kicked on when the generator was already close to capacity. The best models take that in stride, while others bog down or even stall. We also look at how easy it is to move and use a generator, as well as how efficiently it uses gasoline and how long it runs on a single tank.

Safety
Consumer Reports runs each generator through a variety of scenarios designed to capture the ways in which a consumer might inadvertently misuse a generator. We conduct these tests in a custom-built vessel on the grounds of our Yonkers, N.Y., test facility. The vessel is wired with calibrated carbon monoxide sensors, and we record CO levels throughout the container when a generator is on, noting how quickly each generator turns off when the levels become potentially dangerous. For more details, read about how Consumer Reports tests generators for safety.

Generators are sold by power output, as measured in watts. The amount of power they deliver determines how many electronics and appliances you can run at once; figure on about 5,000 watts for a typical home. The delivery and quality of power—both of which we test and score in our generator ratings—determines how well they’ll power your home. A generator with a high output that struggles with power delivery or quality might stall or trip a circuit when it’s bogged down.

Start by making a list of what you don’t want to go without while the power’s down, then add up wattages to get you in the right ballpark. Here are some rough numbers for common essentials:

Refrigerator: 600 watts
Sump pump: 750 to 1,500 watts
Portable heater: 1,500 watts
Window air conditioner: 1,000 watts
Lights: 5 to 80 watts (per bulb)
Computer: 60 to 300 watts

For a more complete list, check out our report on how to pick the right size generator for your house.

To reduce the risk of carbon monoxide poisoning, many new generators feature a built-in sensor that triggers an automatic shutoff if CO builds up to dangerous levels in an enclosed space; some also have engines that emit less CO in the first place. Recent test data from CR shows that this safety feature is likely to save lives.

Consumer Reports only recommends portable generators that pass our expanded CO safety technology test.

Even if your generator has this potentially lifesaving feature, we still advise consumers to follow our long-standing safety guidelines: Always operate a generator a minimum of 20 feet from your home, with the exhaust directed away from any windows, doors, air conditioners, and other structures. 

Don’t let rain, snow, or wind keep you in the dark. Consider these options to make sure you get the best generator for your needs.

Automatic CO Shutoff
This critical safety feature automatically shuts down a generator’s engine if a built-in CO sensor detects that the deadly gas has built up to certain levels. A portable generator must have this feature, and must pass CR’s safety tests, to earn a spot on our list of CR recommended generators. More brands than ever offer models with this technology, including heavyweights such as Generac, Honda, and Ryobi. In fact, we have over a dozen generators in our ratings with a CO safety shutoff. You might see marketing terms such as “CO Guard,” “CO Protect,” “CO Detect,” “CO Shield,” or “CO Sense.” The way to verify whether a generator meets one of the two standards is to look for one of these certifications on the packaging:

• ANSI/UL2201 Certified for Carbon Monoxide Safety
• ANSI/PGMA G300 Certified Safety & Performance

Low-CO Engine
Brands such as Ryobi and Echo are using this type of engine to guard against risk of carbon monoxide poisoning.

Automatic Start
When the power goes off, the generator goes on—without you lifting a finger. This is great if you travel a lot or work far from home, and can’t always get there quickly in an emergency.

Electric Start
Several portable models offer this push-button alternative to the hassle of pull-starting the engine. Just factor in the added cost (around $50) if the battery is not included. Stationary models have automatic starting.

Alternative Fuel Capacity
Most portable models run only on gasoline, though some come equipped to run on a propane tank or natural-gas line and others can be converted with kits.

Fuel Gauge
Especially during long blackouts, you may appreciate the ability to see at a glance how much fuel remains in your portable generator.

Low-Oil Shutoff
If oil falls below minimum levels, the generator shuts down to prevent engine damage. Typically a standard feature on stationary generators, it’s increasingly common on portables.

Multiple Outlets
Four or more let you best use the wattage by spreading the load, though we recommend using these only in an extreme pinch at home, or for when you’re away—at, say, a campsite. See the next section on transfer switches.

Removable Console
This connects to the generator so that you can plug in appliances without running (potentially risky) extension cords outdoors.

What’s that? The short answer: It safely connects a home standby or portable generator to your circuit panel via one cable. Skipping it means you’ll need to use extension cords, which can be dangerous—it’s easy to overload an extension cord, which can cause it to overheat and start a fire. 

And a transfer switch is infinitely more convenient. With a transfer switch, you can power entire circuits in your home with no extension cords. That means essentials without a plug, such as overhead lights, well pumps, and water heaters, can be used freely—if you rely on extension cords, you can power only items with a plug, and even then, you’ll need to connect them to your generator with heavy-duty outdoor-rated extension cords. 

We recommend that you have a licensed electrician install a transfer switch, and you should be prepared to pay from $500 to $900 with labor. With a stationary model, the transfer switch turns on automatically. For portable models, you’ll need to flip a few switches by hand when the power goes out. (Be sure to have your electrician walk you through the procedure.) 

Most transfer switches are designed for a 220-volt input, which means you’re looking at a generator of 5,000 watts or more. Stationary models shut off automatically when the power comes back on; for a portable, you’ll flip the same switches the other way to bring back grid power.

Keep in mind that you’ll need to choose which circuits are connected to the transfer switch. One tip that will make prioritizing easier is to determine which outlets and appliances are controlled by each circuit breaker in your panel, and label them accordingly. The easiest way: Get a small electric device called a digital circuit breaker finder, which you can buy for less than $50. That way, you can make sure the electrician connects the circuits for all your essentials. 

Want to save money? Install an interlock device instead, which costs $100 to $200 less than a transfer switch and can be installed in less time by an electrician. This device allows your generator to power your home’s entire circuit breaker panel, but it also prevents running the generator while you’re getting power from your utility company once your electric service is restored. That’s important because operating a generator while you’re also getting power from your utility company could fry your electronics, and potentially shock a utility worker working near your home.