How Much Power Do I Need? — Generator Buying Guide
When the power goes out, a generator can keep your house warm in winter or cool in summer; it can keep your food cold, your kitchen cooking, and your computers and phone 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—or anyone relying on a generator—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 in a typical home.
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
Pick a Type
You can go one of four 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. And portable power stations are large batteries that store electricity for when you need it, the only option for someone who lives in an apartment, say, and has no way to safely run a generator outdoors.
Home Standby Generators
- These units cost the most 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 typically supply more power than these other options.
- 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.
$3,000 to $6,000
- These units tend to cost less than home standby 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 never in an enclosed space. These models can quickly produce deadly levels of carbon monoxide. Always run a portable generator at least 20 feet away from your home, including equipment such as a central AC condenser or window AC, and direct the exhaust away from your home or any other structure, including the neighbors' home.
- If it's raining, shield your generator with a canopy designed for your particular model.
- Several of these models offer electric starting. The battery required, however, may not be included.
- They provide from 3,000 to 8,500 watts.
$400 to $1,000
Additional Features to Consider
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
A critical safety feature new to portable generators that automatically shuts down the engine if a CO sensor detects levels of the deadly gas building up to certain limits. A portable generator must have this feature to earn a spot on our list of CR recommended products. 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 references on the packaging:
• ANSI/UL2201 Certified for Carbon Monoxide Safety
• ANSI/PGMA G300 Certified Safety & Performance
An additional safety feature brands such as Ryobi are using to guard against risk of carbon monoxide poisoning.
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.
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.
Especially during long blackouts, you may appreciate the ability to check at a glance how much fuel remains in your portable generator.
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.
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.
This connects to the generator so you can plug in appliances without running (potentially risky) extension cords outdoors.