We tested the inverters both in our labs and in the home of a staffer who had lost power—one among millions of northeast homeowners following a Halloween snowstorm. We also consulted the manufacturer and other industry experts.
We found that inverters can keep at least some of your home’s essentials energized. But you’ll need to prioritize: Even the smaller, 900-watt PW900-12 was able to run a freezer, two refrigerators, two sump pumps, lights, and chargers for various electronics for our staffer at home—but not all at once. Fortunately for him, only one of two installed sump pumps needed to come on, and it could do so even when a refrigerator or freezer was also running.
Either inverter supplies enough power to run most circulating hot-water home heating systems. But for other heating systems, you’ll need to weigh your options. A forced-air system might require a larger inverter, and an inverter might not work at all with other heating options. These systems are hard-wired and need to be connected to a transfer switch, installed by an electrician, to power on.
What’s more, knowing both the starting (peak) watts and continuous-load wattage for what you’re powering is especially important with inverters. The rule of thumb for continuous-load wattage is to multiply the amps—as stamped or printed on the device—by 110 volts. But when a device first starts up, its starting load can be two to 10 times that of its continuous load, particularly for sump pumps and refrigerators. That means you may have to lower your expectations with an inverter. or consider stepping up to a full-fledged generator.
Still other inverter caveats are worth considering. For instance, we used a fully charged, spare car battery to run a refrigerator for roughly six hours before the battery ran down. But unless you have an extra battery lying around, you’ll need to keep your car running so the alternator can keep its battery charged. Idling the car with the inverter attached used about a third of a gallon of gasoline per hour; we idled ours for 14 hours one day with no apparent ill effects. But that also means you’ll need to keep the car outdoors with the exhaust facing away from the house and at least 15 feet away to reduce the risk of carbon-monoxide entering the home. And you’ll need a direct connection to your car’s battery terminals; the 12V cigarette-lighter adapter isn’t up to the task.
Other inverter requirements: You’ll need one extension cord per device you power, though if you have more devices than inverter receptacles, you might be able to alternate between, say, a refrigerator and a sump pump. Each cord will need a route from the device to the car. That typically means you’ll have to keep at least one window ajar—an issue when you’re also trying to keep what little heat that remains in the house. (A dryer vent or basement window might be an alternative.)