Generator Buying Guide

To test generators for performance, our expert engineers load each model with various 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 quit. 

We also consider how easy it is to move and use a generator, how efficiently it uses gasoline or other fuel, and how long it runs on a single tank.

We run each generator through a variety of scenarios designed to capture the ways in which a consumer might inadvertently misuse a generator to test for safety. We conduct these tests in a custom-built facility on the grounds of our Yonkers, N.Y., test facility. Our test chamber 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. 

Finally, to reduce the risk of carbon monoxide poisoning, many portable 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, and we’ll only recommend portable generators that pass our expanded CO safety technology test.

Choosing the right home generator means figuring out what size generator you need first. Generators are sold by power output, measured in watts. The amount of power a generator delivers 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 determine how well a model will 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.

Before you look through our generator ratings for the best generator for your home, make a list of the devices you’ll need when the power’s out. Then add up wattages to get you in the right ballpark. 

Here are some rough wattage estimates for common essentials as you build out your list:

• 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

Don’t let rain, snow, or wind keep you in the dark. Look for these options to get a generator that’s safe, reliable, and tailored to your power 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 reached certain levels. We have over a dozen generators in our ratings with a CO safety shutoff. (CR only recommends portable generators with this feature.)

From Generac to Honda, more brands than ever offer options with this technology—you might see them advertised with marketing terms like “CO Guard” or “CO Protect.” But the only 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 including Ryobi and Echo are using a low-CO engine to guard against carbon monoxide poisoning.

Automatic Start
When the power goes off, the generator automatically starts—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 electric start, a push-button alternative to the hassle of pull-starting the engine. If the battery is not included, make sure you factor in the added cost (around $50). 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
You may appreciate glancing at a fuel gauge to determine what fuel is left in your portable generator, especially during blackouts.

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

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

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

A transfer switch is infinitely more convenient than an extension cord and allows you to safely connect a home standby or portable generator to your circuit panel via one cable. Without a transfer switch, you’ll need to use an extension cord, which can be easily overloaded and cause it to overheat and start a fire.

Using a transfer switch means you can power essentials without a plug (overhead lights, well pumps, and water heaters, for example), while relying on extension cords means you can power only items with a plug. Even then, you’ll need to connect them to your generator with heavy-duty outdoor-rated extension cords.

Here are a few important notes on transfer switches:

• We recommend that you have a licensed electrician install your transfer switch for around $500 to $900. Your electrician can also walk you through turning your switch on and off.
• With whole-house generators, the transfer switch turns on and turns off automatically when the power shuts off or goes on, respectively. For portable models, you’ll need to flip a few switches by hand when the power goes out and switch them back to bring back grid power.
• Most transfer switches are designed for a 220-volt input, which means you’ll need a generator of 5,000 watts or more.
• Keep in mind that you’ll need to choose which circuits are connected to the transfer switch. To do so, get a digital circuit breaker finder to determine which outlets and appliances are controlled by each circuit breaker in your panel. Then label them accordingly so that the electrician connects the circuits for all your essentials.