Can A Pint-Sized Power Inverter Replace A Generator?

Looking for some low-cost power backup? Given recent storms and the growing number of blackouts, you certainly have company—and perhaps fresh memories of spoiled food, a flooded basement, no heat or air conditioning and (if you have well water) no water for bathing or household chores.

Once you’ve decided you’ve had enough and start researching generators, you’ll find two clear choices. Portable generators for home use start at about $300 and can power selected devices using multiple extension cords or, using a transfer switch, a single plug-in connection you make when the main power goes out. The price goes up if you want your generator to kick in automatically when you lose power: Figure on at least $2,500-plus before installation for a standby, or whole-house, generator that can also handle larger needs. 

Suppose all you want to do is keep the sump pump in your basement going or keep your food cold during short-term outages: You might get by with a power inverter. These devices start at under $100 and essentially use your car as a generator, which was the premise for our tests during a freak snowstorm over the 2011 Halloween weekend that caused broad power outages along the nation’s northeast coast. 

We tested two models from PowerBright, a brand sold in home centers, warehouse clubs, and other retailers such as Sears and Walmart. The PW900-12, $80, provides 900 watts (1,800 peak) and 7.5 amps; the PW1500-12, $180, is rated for 1,500 watts (3,000 watts peak) and 12.5 amps. Both have two three-prong receptacles and claim to be safe for powering laptops, televisions, gaming consoles, and other electronics.

What’s an inverter?

An inverter resembles a rectangular box about the size of shoe box. At one end are wires for connecting to a power source; at the other are AC receptacles. An inverter takes in direct-current (DC) power—in this case, from your car’s 12-volt system—and converts it to the alternating-current (AC) power required by refrigerators, sump pumps, and most other household devices. 

That DC to AC conversion isn’t as simple as it sounds, however. AC-powered devices are designed to run on current that alternates smoothly. Because many inverters don’t supply a pure sine wave—and those that do typically cost as much as a more-capable generator—anything you power with an inverter is likely to run less efficiently.  

Once you’ve powered a couple of devices, you might be tempted to plug a half-dozen more into a power strip and then plug the strip into the inverter to increase your options. But unless you’re just charging iPods and cellphones, it probably won’t work and wouldn’t be a good idea. The reason: The inverter can’t draw more from your car’s battery than the alternator can replenish without draining the battery.

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