What Can You Run During a Power Outage on Battery Backup?

Written By Wesley Cronk

A mid-sized portable power station or home backup battery can keep your essentials running during an outage: a refrigerator, Wi-Fi and phones, lights, a CPAP machine, and small kitchen appliances. What it can’t do, without a much larger professionally installed system, is run central air conditioning, electric water heaters, or an electric range. The honest answer comes down to two numbers: how many watts your devices draw at once, and how many watt-hours of storage your battery holds.

The short answer

Think of it in two tiers. A compact unit (roughly 300 to 800 watt-hours) covers the connect-and-comfort tier: phones, a laptop, a Wi-Fi router, a few LED lights, and a CPAP overnight. A larger station or home battery (1,500 to 5,000-plus watt-hours) adds the keep-food-cold tier: a full-size refrigerator, a sump pump, and intermittent use of a microwave or coffee maker.

The limit usually isn’t whether a battery can run a device. It’s how many devices it can run at the same time, and for how long.

A realistic wattage guide

Here’s what common household items draw. Running watts are continuous; starting (surge) watts are the brief spike when a motor or compressor kicks on:

  • LED light bulb: 8 to 15 watts

  • Wi-Fi router or modem: 15 to 40 watts

  • Phone or laptop charging: 5 to 90 watts

  • CPAP without a heated humidifier: 30 to 60 watts

  • Refrigerator: 300 to 800 running watts, up to about 1,800 to start

  • Sump pump (one-third to one-half HP): 600 to 900 running watts, 1,800 to 2,500 to start

  • Microwave (1,000-watt class): 1,000 to 1,500 watts

  • Coffee maker: 600 to 1,200 watts

  • Space heater: about 1,500 watts

  • Central AC or electric range: 3,000 to 5,000-plus watts

Two takeaways. First, motors and compressors, like fridges, sump pumps, and well pumps, need a surge of two to four times their running watts for a second or two, so your battery’s inverter has to handle that peak, not just the average. Second, anything that makes heat, like space heaters, electric ranges, water heaters, and hair dryers, is a power hog and will drain a battery fast.

The two numbers that decide everything

Watts (power) tell you what you can run at once. Watt-hours (energy) tell you how long. A battery rated at 1,000 watt-hours can, in theory, deliver 1,000 watts for one hour, 500 watts for two hours, or 100 watts for ten hours.

A rough runtime estimate: usable battery watt-hours divided by total watts in use is roughly your hours of runtime.

Most batteries deliver about 85 to 90 percent of their rated capacity after inverter losses, so multiply by about 0.9 before you divide. Example: a 1,000 watt-hour station running a 60-watt CPAP overnight gives about 15 hours, comfortably through the night. The same station trying to run a 700-watt fridge continuously would last barely over an hour, but because a fridge only runs about a third of the time, real-world runtime stretches to roughly four hours.

What it won’t run (and why)

Large 240-volt loads, like central air conditioning, electric water heaters, electric ranges and ovens, electric clothes dryers, and EV chargers, are beyond what a plug-in portable battery is designed for. These need either a whole-home battery wired in by a licensed electrician or a standby generator. If running those during an outage is the goal, that’s a different and bigger decision.

How to size it to your needs

Start with your must-run list, not the catalog. Add up the running watts of everything you’d want on at the same time, then confirm the battery’s continuous and surge output clear that number. Next, decide how many hours you need to cover and multiply by your total draw to find the watt-hours you need. Our guide to sizing a portable power station walks through this step by step, and if you’re still deciding between a portable unit and an installed battery, see portable power station vs. home backup battery.

The Fortify approach is vendor-neutral: we help you buy the right-sized unit for your actual must-run list, not the biggest box on the shelf. See how we work, browse options on the Shop page, or dig into the Resources library.

Frequently asked questions

Can a portable power station run a refrigerator?

Yes. Most mid-sized stations (1,000 watt-hours and up) can run a typical refrigerator, as long as the inverter handles the compressor’s startup surge of up to about 1,800 watts. Expect several hours of runtime per charge, since fridges cycle on and off rather than running constantly.

How long will a battery power my CPAP?

A 500 to 1,000 watt-hour battery will typically run a CPAP for one to two nights without a heated humidifier. Turning off heated humidification and heated tubing extends runtime significantly, since those features can double or triple the machine’s draw.

Can I run my whole house on a battery?

Not with a portable unit. Whole-home backup, including central AC and 240-volt appliances, requires a home battery system installed by a licensed electrician, or a standby generator. Portable batteries are designed for essential circuits and plug-in loads.

How do I calculate runtime?

Multiply the battery’s rated watt-hours by about 0.9 (for inverter losses), then divide by the total watts you’re running. That gives an approximate runtime in hours; appliances that cycle, like refrigerators, will run longer than the raw math suggests.

By the Fortify Resilience Desk. Fortify is a vendor-neutral resilient-power company that helps real estate owners and households buy right-sized, code-compliant backup power.

Sources: U.S. Department of Energy (Energy Saver), EnergySage, and Enphase.

Wesley Cronk
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