Generator buying guide

Last updated: October 2015

Getting started

Blackouts needn't lead to spoiled food and nights by flashlight. Consumer Reports' generator tests show that you can start powering a houseful of lights and appliances for less than $700. But as we found, some important components cost extra.

We focused on moderately priced portable and stationary models that deliver 5,000 to 7,000 watts, enough for most needs. But we also tested some larger models that deliver more power. Portables cost the least and can be stored in a garage or shed when you don't need them. One lower-priced model we tested powered refrigerators, well pumps, and other home gear almost as well as a more expensive top-scorer.

Stationary models install permanently outside your home and start automatically when needed. And because they run on propane or natural gas instead of gasoline, they offer extended or unlimited run time.

Buying a generator is just the beginning. Many models don't come with parts that you'd think would be included with the price. And some could let you down when you need them most or put an added stress on appliances. Here are the details.

Reliability matters

Generators are typically sold by wattage. How much they put out determines not only how many lights and appliances you can run at once but how well they run. For example, a refrigerator often requires about 600 watts, a portable heater 1,500 watts, a window air conditioner 1,000 watts, and lights 60 to 200 watts. Our wattage calculator provides an average wattage rating for most appliances and devices to help you to tally your needs.

"Batteries not included" applies. Several portables offer electric starting. But the battery required for that feature usually costs an extra $50. And if you think all portables have wheels, think again: They were a $150 option on one model we tested.

Some slipped when demand surged. All of the tested generators met their basic wattage claims. Manufacturers also make higher surge-wattage claims for the extra power needed when refrigerators, air conditioners, and pumps cycle on. Subpar surge wattage lowered the power-delivery scores of some models in our tests.

Some can overheat appliances. Our power-quality test judges the ability to deliver the 120 volts that home circuits usually need. Most met that challenge although one model was more than 10 volts shy under a heavy load and voltage from another was also low--and slightly uneven. Both conditions make motorized appliances and some electronics run hotter.

How to choose

Decide what you really need to power. If that includes a central air conditioner or an electric dryer or oven, you'll need a larger generator. Here's what else to keep in mind:

Count on a transfer switch. It costs about $500 to $900 installed and connects a portable generator to your home's circuit box as with a stationary model. In addition to eliminating the risk and hassle of extension cords, the switch protects the generator and appliances from damage when grid power returns and keeps the generator from endangering technicians working on the power lines.

Think about the fuel. If they're running 24/7, most portables use roughly 8 to 22 gallons of gasoline a day, compared with four to eight 20-pound tanks of propane for portable models. (A 250-gallon tank for stationary units can run 8 to 15 days around the clock.) Buying and storing lots of fuel before a storm can be unwieldy, although you can pour unused gasoline into your car's gas tank.

Look for smart features. Most of the portable generators in our tests turn themselves off when engine oil is low. And the fuel shutoff on all tested gasoline models lets you run the engine dry to draw gas out of the fuel system to keep it from fouling parts if it degrades during storage.

Play it safe

Powering too many appliances will trip the generator's circuit breakers, causing power loss. Be sure what you're powering is within the generator's rated wattage; most transfer switches make that easier by showing wattage levels.

And protect against carbon monoxide, which kills about 86 people each year--and sends thousands more to the emergency room. Run any generator outdoors and away from the house, far from doors, windows, and anywhere else air enters the house. Never run it in a basement or garage; even with the garage door open, it can endanger people inside the house.


Knowing what you're powering is the first step to choosing the right generator. Here are the types of generators and their pros and cons.

Portable generators

These small and midsized models typically put out anywhere from 3,000 to 8,500 watts. They cost from $400 to $1,000 and are adequate for many homes, which is why they're the biggest sellers. Most portables run only on gasoline, but some can also use liquid propane or connect to a natural-gas line.


They cost the least and are relatively easy to move and store. And they're adequate for powering common plug-in appliances and lights.


Portables don't provide nearly enough power for heavy drains like central air conditioning. And for most, you'll have to store large quantities of gasoline, which, besides being hazardous to store, also degrades over time.

Stationary generators

These large models mount permanently outside the house and are growing in popularity. Their roughly 5,000 to 20,000 watts let the largest power an entire house, including central heat and air conditioning.


In addition to providing plenty of watts, stationary generators can power a bevy of hardwired items, eliminating the hassle and risk of running power cords. Most run on either propane or natural gas, eliminating the risks of pouring and storing gasoline. They also run periodic self-diagnosis routines, and a few have optional features that can notify you--say, by sending a text--if service is required.


All of that power and convenience comes at a price ($5,000 to $10,000 for the largest models). Stationary generators also require professional installation, which can add thousands to the overall cost.


Portable generators are the biggest sellers. But whatever you buy, make sure its features help make it safe and easy to use. Here are the generator features to consider:

Alternative-fuel capability

Stationary generators typically run on either propane or natural gas. Most portable models run only on gasoline, though some come equipped to run on a propane tank or natural-gas line--or can be converted with kits.


A single person can move a portable generator with wheels, but you'll still need two people to lift it off the ground--say, for transport. Note that a few generators price wheels separately, as an option.

Low-oil shutoff

This feature protects the engine from damage by shutting down the generator if the oil level falls below the minimum. It's typically on stationary generators and on an increasing number of portables.

Fuel gauge

The gauge lets you check a portable's fuel tank at a glance. It's especially useful during a prolonged power failure.

Electric start

Portable generators with a battery-powered, pushbutton starter save you the hassle of pull-starting the engine. But we've found pull-start models relatively easy to start. Your best bet: Look for electric start with a pull cord as an option since the electric-start feature's battery needs occasional charging. Stationary models have automatic electric start.

Inverter technology

A feature of some higher-end portables, it makes wattage output smoother and more consistent via a microprocessor-controlled circuit. The best inverter generators in our Ratings also tend to be the quietest in our tests. Engine speed is measured in revolutions per minute (RPM), and the higher the RPM the higher the sound pressure--the loudness of what you hear. Engines of conventional generators run at a constant 3,600 RPM regardless of the power demand. But inverter generators can run at a lower RPM during lower power demands, and at those lower speeds the noise output is lower. (They also use less fuel at these lower speeds.) Those we've tested are also fully enclosed and have better mufflers to reduce the noise even further.

Multiple outlets

Four or more outlets let you best use a generator's wattage by spreading the load through more outlets--important if you're using extension cords instead of a transfer switch. For safety, we recommend you spring for a transfer switch.

Wattage requirements

Wattage ranges: How much machine do you need?

How much generator should you buy? Here's what different sizes can power. Pick a model with a wattage at least equal to the total for what you're powering. Manufacturers also suggest totaling the higher surge watts some appliances draw when they cycle on. Models that scored well for power delivery were up to that surge; for untested models, we suggest simply focusing on running watts. To determine your needs, use our wattage calculator.

Small portable (110-volt), 3,000 to 4,000 watts

What it powers. The basics, including such items as:

  • Refrigerator (600 watts)
  • Microwave (1,500 watts)
  • Sump pump (600 watts)
  • Several lights (400 watts)
  • TV (200 watts)

Price range. $400 to $800 for most; more for inverter models.

Midsized portable and small stationary (220-volt), 5,000 to 8,500 watts

What it powers. Same as small models, plus:

  • Portable heater or well pump (1,300 watts)
  • Computer (250 watts)
  • Heating system (500 watts)
  • Second sump pump (600 watts)
  • More lights (400 watts)

Price range. $500 to $1,000 for portables; twice that for stationary.

Large portable (220-volt), 10,000 watts

What it powers. Adds choice of:

  • Small water heater (3,000 watts)
  • Central air conditioner (5,000 watts)
  • Electric range (5,000 watts)

Price range. $2,000 to $3,000.

Large stationary (220-volt), 10,000 to 15,000 watts

What it powers. Same as large portable models, plus:

  • Clothes washer (1,200 watts)
  • Electric dryer (5,000 watts)

Price range. $5,000 to $10,000 or more, plus installation.

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