Generator Buying Guide

When the power goes out, a generator can keep your house warm or cool, your kitchen cooking, and your computers and phones charging. Assuming you have one.

People tend to buy generators around major storms, when they’re prone to making a desperate decision—without a plan for what to do when they get it home. Working by flashlight, in a rush to get the power up and running, they might skip over critical safety steps during setup. And people die every year from carbon monoxide poisoning related to generators.

We don’t want you to be one of those people.

Know Your Power Priorities

Generators are sold by power output, as measured in watts. The amount of power they deliver determines how many lights and appliances you can run at once; the quality and consistency of that power determines how well they'll run. Figure on about 5,000 watts to cover the basics.

Start by making a list of what you don't want to go without while the power's down, then add up their watts 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: 60 to 600 watts
Computers: 60 to 300 watts

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

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: a small electric device called a digital circuit breaker finder, which you can buy for less than $50. 

Pick a Type

You can go one of three ways. Home standby generators are installed permanently, can run on natural gas or propane, and kick on automatically during an outage. Portable and inverter generators can both be moved around, though they come in different sizes. Some are better for transporting to a tailgate, while others are better kept on your property as a backup power source. 

A standby generator.

Home Standby Generators

• These units cost more money and should be installed by a pro (so factor in labor costs). An experienced electrician can help with town or municipal permits, noise restrictions, and proper location.

• These start automatically when the power goes out, and often supply more power.

• They run a self-diagnosis and let you know when maintenance is needed. Some even do this via email or text, to you or your dealer.

• You have your choice of fuel— propane, which is less risky to store than gasoline, or natural gas, which provides an unlimited supply of power. 

• They range from roughly 5,000 to 20,000 watts. 

Typical cost:
$3,000 to $6,000

Home Standby Generator Ratings
A portable generator.

Portable Generators

• These units tend to cost less than home standy generators.

• They typically run on gasoline that you may need to store in large quantities. Stabilizer must be added to your fuel for prolonged storage. 

• You can use portable generators anywhere on or off your property, but they must be at least 20 feet away from any structure, including your house, doors, or windows—and not in an enclosed space. Make sure the exhaust is facing away from your house. These models produce potentially deadly levels of carbon monoxide, a gas that kills approximaely 149 people each year in the United States. If it's raining, you must use a tent or cover.

• Several of these models offer electric starting. The battery required, however, may not be included.

• They provide from 3,000 to 8,500 watts.

Typical cost:
$400 to $1,000

Portable Generator Ratings
An inverter generator.

Inverter Generators

• Because their engines are more complex, these models generally cost more than portable generators of a comparable output. 

• Inverter generators are much quieter than their conventional counterparts because they throttle up and down to match demand rather than run at full power all the time. They also have more sophisticated exhaust systems which also help tamp down noise.

• They run more efficiently and produce fewer emissions, but you should still follow all the same safety precautions you would with a portable generator. 

Typical cost:
$500 to $4,000

Inverter Generator Ratings
A portable power station.

Portable Power Stations

• These power storage devices  don’t use gas or propane—they’re powered by a battery that you can charge by plugging into an electrical outlet or sometimes an included solar panel (you might also see them for sale as “solar generators”).

• Portable power stations are relatively new to the market, and they typically cost more than portable gas generators.

• For those concerned about noise, note that these machines are all extremely quiet, and in our tests earn Excellent ratings for noise.

• They don’t produce fuel emissions/carbon monoxide, so you can use them indoors.

• Don’t expect to power as many appliances or run them for an extended time, since they don’t output as much power as portable generators and can’t be refilled without electricity.

• They don’t require anything to start—think of it as a large battery pack for your cell phone.

Typical cost:
$750 to $3,000

Portable Power Stations Ratings

Features That Count

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 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 check 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 lets 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 a campsite. See the next section on transfer switches.

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

Yes, You Need a Transfer Switch

What's that? The short answer: It safely connects a home standby or portable generator to your circuit panel via one cable. Skipping it could endanger utility workers, cause appliances to fry, and damage the generator itself.

We recommend that you have a licensed electrician install it, 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. For stationary models, it shuts off when the power goes on; for a portable, you'll flip the same switches the other way to bring up live power.

Want to save money? Install an interlock device instead, which costs $100-$200 less than a transfer switch and can be installed in less time by an electrician. This covers your service panel's main cutoff switch—so when the power pops back on, you can't accidentally put the generator on. Because that would be a bad thing. 

A portable generator hooked up to an electrical panel via a transfer switch.
Illustration: Chris Philpot

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