How Big a Portable Power Station Do You Need for a Power Outage?

Short answer: size a portable power station twice. First check that the station's continuous AC output (watts) covers everything you want running at the same moment, plus the brief starting surge of a fridge or freezer. Then check that its capacity (watt-hours) covers how long you want those things to run. A refrigerator, a Wi-Fi router, two LED lamps and two phone charges add up to about 1,600 Wh for one day in our worked example, which points to a station rated near 2,000 Wh.

ChartBar chart of a one-day outage energy budget: refrigerator 1,233 Wh, Wi-Fi router 240 Wh, two LED lamps 100 Wh, two phone charges 30 Wh, total 1,603 Wh, divided by 0.85 gives about 1,886 Wh of rated capacity

Original VoltLore diagram. Example numbers; replace them with your own appliance labels.

Step 1: List what has to keep working

Write down only the things you would actually run in an outage. For most homes that is the refrigerator, internet, a few lights and phone charging; some add a fan or a laptop. Leave out space heaters, electric cooktops, hair dryers and window air conditioners at the start: each can draw well over 1,000 W, and they empty a battery fast.

For each item, find the wattage. It is usually printed on the label or nameplate. If the label lists only amps, multiply amps by volts (120 V for ordinary US outlets) to get watts, as the Virginia Cooperative Extension energy guide explains.

Step 2: Check output watts, including the starting surge

Add the running watts of everything that might be on at once. The station's continuous AC rating has to be higher than that total.

Anything with a compressor or motor (refrigerators, freezers, some pumps) needs a short burst of extra power when it starts. Check the appliance manual or ask the manufacturer for the starting figure, and compare it with the station's surge or peak rating. A station that covers the running watts but not the starting surge will shut off each time the compressor kicks in.

Step 3: Work out watt-hours for the time you need

Energy is watts multiplied by hours. A 10 W router running for 24 hours uses 240 Wh. Two 10 W lamps for five hours use 100 Wh.

Refrigerators are the exception, because the compressor cycles on and off. Don't multiply the nameplate wattage by 24. Two better options:

• Use the yellow EnergyGuide label. It gives estimated kWh per year. Divide by 365: a 450 kWh/year refrigerator averages about 1.23 kWh (1,233 Wh) a day.
• Use the cycling rule of thumb. The Virginia Cooperative Extension guide suggests dividing the time a refrigerator is plugged in by three to estimate how long it runs at full wattage.

Add the daily figures together. In our example the total is 1,603 Wh.

Step 4: Add an allowance for losses and reserve

Turning battery power into 120 V AC through the inverter costs some energy, and running a battery right down to zero is rarely practical. We divide by 0.85 as a planning allowance. That is our editorial assumption, not a measured figure; if the manufacturer publishes an AC efficiency figure, use theirs.

1,603 Wh ÷ 0.85 ≈ 1,890 Wh. So a station rated around 2,000 Wh covers our example day with a small margin. Cold weather also reduces how much energy a battery delivers, so allow more if the station will sit in a cold garage.

How long should a portable power station last in an outage?

Outage length varies a lot by place and year. The U.S. Energy Information Administration reports that customers averaged about 11 hours of interruptions in 2024, nearly twice the average of the previous decade, mostly because of Hurricanes Beryl, Helene and Milton. Outages not caused by major events average about two hours a year, while customers in South Carolina averaged nearly 53 hours in 2024.

Use your own history: if your street usually loses power for an evening, a smaller station is enough; if storms take you out for days, plan on recharging (solar panels or a car) rather than buying an enormous battery.

These rows are arithmetic from the example devices, not test results. Your appliances will differ.

Do you need to run the refrigerator at all?

Maybe not for short outages. FoodSafety.gov says a refrigerator keeps food safe for about 4 hours if the door stays closed, and a full freezer holds its temperature for about 48 hours (24 hours if half full). Discard refrigerated perishables that have been above 40 °F for more than 2 hours. A power station is most useful when the outage will clearly outlast those windows.

Frequently asked questions

Can a portable power station run a refrigerator? Yes, if its continuous output covers the fridge's running watts, its surge rating covers the starting load, and its capacity covers the hours you need. Check all three, not just capacity.

How many watt-hours does a refrigerator use in a day? Divide the kWh/year figure on its EnergyGuide label by 365. A 450 kWh/year model averages about 1,233 Wh a day; older or larger models use more.

Can I use a power station indoors? Battery power stations don't burn fuel, so they produce no exhaust; follow the manufacturer's manual for placement and ventilation. Gas generators are different: CDC says to use them outside and at least 20 feet from doors, windows and vents. We compare the two in Portable Power Station vs Gas Generator.

Does battery chemistry change the sizing? Not the arithmetic, but it changes weight, lifespan and cold-weather charging. See LiFePO4 vs NMC.

How we researched this

VoltLore has not tested a specific power station for this guide. The worked example uses round numbers and a published appliance-energy method; the 0.85 allowance is our assumption and is labeled as such. Last checked October 17, 2026.

Sources

• Virginia Cooperative Extension, Estimating Appliance and Home Electronic Energy Use — watts × hours ÷ 1,000 formula, amps × volts, refrigerator cycling note.
• U.S. Energy Information Administration, Hurricanes in 2024 led to the most hours without power in 10 years — 11 hours average in 2024, about two hours for routine outages, nearly 53 hours in South Carolina.
• FoodSafety.gov, Food Safety During Power Outage — 4 hours (refrigerator), 48/24 hours (freezer), 40 °F threshold.
• CDC, Prevent Carbon Monoxide Poisoning — generators outdoors, at least 20 feet from doors, windows and vents.