Best portable and stationary generators

Blackouts like the one that crippled the East Coast last June needn't lead to spoiled food and nights by flashlight. Our latest 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. Portables cost the least and can be stored in a garage or shed when you don't need them. Generac's GP5500 5939, a CR Best Buy at $670, powered refrigerators, well pumps, and other home gear almost as well as the pricier, top-scoring Troy-Bilt.

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. Generac was also the value leader in this group; its CorePower 5837, a CR Best Buy at $1,800, performed capably for far less than the top-rated Kohler we tested.

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

"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're a $150 option on the Yamaha 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 fridges, air conditioners, and pumps cycle on. Subpar surge wattage lowered the power-delivery scores for the All Power APG3560, Gentron GG3203, and Briggs & Stratton 30468.

Two could overheat appliances. Our power-quality test judges the ability to deliver the 120 volts that home circuits usually need. Most met that challenge. The Generac XG7000E 5798 was more than 10 volts shy under heavy load. Voltage from the stationary Briggs & Stratton EmPower 040301 was also low—and slightly uneven. Both conditions make motorized appliances and some electronics run hotter.

One model came with glitches. Two samples of the portable ETQ PG60B12 started and idled without delivering power. We called the company and found that some left the factory improperly adjusted. A wrench and screwdriver got them working, though performance was just so-so.

Decide what you really need to power. If that includes a central air conditioner or an electric dryer or range oven, you'll need a larger generator than the ones we tested. 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. 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.) Buying and storing lots of fuel before a storm can also be unwieldy, though you can pour unused gasoline into your car's gas tank.

Look for smart features. All but the portable Troy-Bilt 6000 and Briggs & Stratton 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. Minimize carbon-­monoxide risks: Run generators outside—as far from the house as possible and never indoors.

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. User our wattage calculator to determine how much power you need.