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Small house at night with warm lights glowing in the windows while the street around it is dark

Outage backup

Lights out on the street. Not in your kitchen.

Two days of fridge, Wi-Fi, lights and phones take about 6.5 kWh of battery. Add a well pump, furnace blower, freezer or CPAP and see what size you need, and what winter sun adds back.
Size my backupWinter solar by state

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2.7 kWh

An essentials day

Fridge, Wi-Fi, 4 LED bulbs, 2 phone charges

4 hours

Food safe in a closed fridge

48 hours in a full freezer (Ready.gov)

880 Wh

From 400 W of panels, December

Maryland, PVWatts model

What you need to keep running

1. What must keep running
  • Refrigerator2.3 kWh
  • Wi-Fi router (10 W)240 Wh
  • LED light bulb (9 W)180 Wh
  • Phone charge (15 Wh each)30 Wh
  • Chest or upright freezer—
  • CPAP with heated humidifier (28 W)—
  • Well pump (1/3 HP, 1,000 W)—
  • Furnace blower fan (1/3 HP, 700 W)—

Hours are example settings. A furnace blower runs more on cold days; a well pump runs while you use water.

2. How long is the outage?
4. Solar panels to recharge with

You use

2.7 kWh a day

Battery for 2 days, no recharging

6.5 kWh

2.7 kWh × 2 ÷ 85% usable. It must also put out at least 790 W at once, and up to 2,990 W for a moment when a motor starts (a generator-sizing worst case; check the station's surge rating).

Cheapest power stations that cover it

Recharging from 400 W of solar in December

About 880 Wh a day in Maryland: 32% of what you use. Covering all of it takes about 1,250 W of panels.

Kits you can buy for a 2-day outage

Complete kits from each brand's own store: the power station, batteries and that brand's own panels. One button puts every item in the brand's cart; you review and check out on their site. Prices checked Oct 26, 2026 and they change.

Disclosure: We may earn a commission if you buy through these links. It never changes our recommendations. How we make money.

*Prices and specifications are from each manufacturer's US website, checked , . Prices change often, sometimes daily during sales; the seller's page is the final word. Cycle ratings are the maker's own figures, measured to different end points, so treat them as rough guides.

How the calculation works

Daily use = watts × hours a dayfor each load (the US Department of Energy method). Fridges and freezers use the EIA's average yearly use divided by 365, because they cycle on and off.

Battery = daily use × days ÷ 85%. We count 85% of a power station's rated capacity as usable after inverter losses, the same figure we use across the site.

Output = running watts of everything at once + the biggest motor start, the method in EWEB's generator sizing sheet. We match stations on continuous output and, where the maker gives one, surge rating.

If your well pump or furnace blower is wired into the house, power it only through a properly rated transfer switch installed by an electrician.

Just the fridge? See power stations for a refrigerator. A CPAP? See power stations for a CPAP. The whole house? See home battery backup.

Winter solar recharge by state (400 W of panels)

What 400 W of panels adds a day in December, the darkest month, against an essentials day of 2.7 kWh. Most sun first.

December solar recharge from 400 watts of panels by state
StateA December dayShare of essentials
Hawaii1.6 kWh59%
New Mexico1.5 kWh54%
Arizona1.4 kWh52%
California1.4 kWh50%
Nevada1.4 kWh50%
Colorado1.2 kWh45%
Oklahoma1.2 kWh44%
Florida1.2 kWh44%
Louisiana1.2 kWh43%
Kansas1.2 kWh43%
Texas1.2 kWh42%
Wyoming1.1 kWh40%
South Carolina1.1 kWh40%
Mississippi1.1 kWh40%
North Carolina1.1 kWh38%
Arkansas1.0 kWh38%
Georgia1.0 kWh37%
Alabama1.0 kWh37%
Missouri1.0 kWh36%
Utah999 Wh36%
Virginia997 Wh36%
District of Columbia948 Wh35%
Nebraska932 Wh34%
Tennessee928 Wh34%
Iowa883 Wh32%
Maryland880 Wh32%
Delaware874 Wh32%
Pennsylvania872 Wh32%
South Dakota852 Wh31%
Massachusetts831 Wh30%
New Hampshire826 Wh30%
New York819 Wh30%
New Jersey815 Wh30%
Rhode Island801 Wh29%
Kentucky800 Wh29%
Montana785 Wh29%
Maine778 Wh28%
West Virginia775 Wh28%
Connecticut759 Wh28%
Indiana742 Wh27%
Ohio734 Wh27%
Illinois733 Wh27%
North Dakota688 Wh25%
Minnesota675 Wh25%
Idaho670 Wh24%
Wisconsin622 Wh23%
Michigan583 Wh21%
Vermont581 Wh21%
Oregon506 Wh18%
Washington453 Wh16%
Alaska92 Wh3%

PVWatts model for 1 kW of south-facing panels at a 20 degree tilt near one city per state, scaled to 400 W. Portable panels laid flat or shaded make less.

Running a generator instead?

A generator covers long outages and big loads, but it must run outdoors, at least 20 feet from the house (Ready.gov, CDC). See how much fuel to store with the generator runtime calculator.

Frequently asked questions

What size power station do I need for a power outage?

Add up what you need a day, multiply by the days, and divide by 85% for the share you can use. A fridge, Wi-Fi, four LED bulbs and two phone charges use about 2.7 kWh a day, so two days takes about 6.5 kWh. Add a well pump and a furnace blower and it rises to about 7.9 kWh a day.

Can a power station run a well pump or a furnace?

Often, if it is big enough. A 1/3 HP well pump runs at about 1,000 W and needs about 2,000 W more for a moment to start; a 1/3 HP furnace blower runs at about 700 W (EWEB generator sizing sheet). With the essentials too, the station must put out about 2,490 W and handle about 4,690 W at start-up. If they are wired into the house, power them only through a transfer switch installed by an electrician (NFPA).

How long will food last in the fridge without power?

About 4 hours in a closed fridge and about 48 hours in a full freezer (Ready.gov, FoodSafety.gov). Ready.gov says to throw away food that has been at 40°F or higher for two hours or more. Keep the doors shut, and you can run the fridge in shifts from a power station to stretch the battery.

Can solar panels recharge a power station in winter?

Yes, but less than in summer. In December, 400 W of panels makes about 880 Wh a day in Maryland in the PVWatts model: 32% of an essentials day. In Hawaii it is about 1.6 kWh, in Alaska about 92 Wh.

How much battery does a CPAP need in an outage?

About 224 Wh a night with the heated humidifier on (28 W for 8 hours, ResMed), about 88 Wh a night (11 W) without it. See our guide to the best power station for a CPAP for nights per dollar.

Estimates only. Real use depends on your appliances, the weather and how often doors open. Prices and specifications are copied from makers' US websites on the dates shown and change often. See our disclaimer.

Sources

  1. US DOE Energy Saver, Estimating appliance and home electronic energy use (archived copy) — watts × hours a day ÷ 1,000 = kWh a day
  2. EIA Residential Energy Consumption Survey 2020, table CE4.6.EL.ST — refrigerators: 839 kWh a year per household
  3. EIA Residential Energy Consumption Survey 2020, table CE5.3b (detailed electricity end use) — separate freezers 570 kWh, most-used TV 210 kWh, microwaves 107 kWh a year per household
  4. Eugene Water & Electric Board, Generator sizing considerations — running and starting watts: well pump 1/3 HP 1,000 W (+2,000 W to start), furnace fan blower 1/3 HP 700 W (+1,400), refrigerator/freezer 700 W (+2,200), microwave 1,000 W, laptop 60 W, phone charger 20 W
  5. ResMed battery guide (AirSense 10) — 28 W with heated humidifier, about 11 W without
  6. US DOE Energy Saver, Energy efficient lighting fact sheet (2021) — a 1,100-lumen LED screw-in bulb uses as little as 9 W
  7. EnergySage, How many watts does a Wi-Fi router use? — 5 to 20 W; we use 10 W
  8. TidBITS, iPhone battery-life tables — iPhone 16 battery 13.84 Wh; we use 15 Wh a charge to allow for charging losses
  9. Ready.gov, Power outages — fridge keeps food cold about 4 hours, a full freezer about 48; throw out food at 40°F or higher for 2 hours; generators at least 20 ft from windows, doors and attached garages; CO detectors on every level
  10. FoodSafety.gov, Food safety during power outages — 4 hours in a closed fridge, 48 hours in a full freezer
  11. PVWatts v8 solar model (National Laboratory of the Rockies, formerly NREL, run via its PySAM package) on NASA POWER hourly weather — monthly output per kW by state, average of 2015-2024 hourly weather; 1 kW DC fixed roof mount, 20 degree tilt, facing south (180 degrees), standard module, 14% system losses, 96% inverter efficiency, DC/AC ratio 1.2 (PVWatts defaults except tilt). Checked against the PVWatts web API for eight states: within 8%, 3% on average.
  12. NFPA, Generator safety tip sheet (copy hosted by the Village of Penn Yan) — never in an attached garage; CO alarms; cool before refueling; fuel in labeled containers outside living areas; transfer switch by a qualified electrician
  13. CDC, Prevent carbon monoxide poisoning — at least 20 ft from the house, away from doors, windows and vents; install a battery-operated CO detector
  14. EcoFlow RIVER 3 Plus product page — checked October 15, 2026
  15. EcoFlow DELTA 3 product page — checked October 15, 2026
  16. EcoFlow DELTA 3 Plus product page — checked October 15, 2026
  17. EcoFlow DELTA 3 Max product page — checked October 15, 2026
  18. EcoFlow DELTA 3 Max Plus product page — checked October 15, 2026
  19. EcoFlow DELTA Pro 3 product page — checked October 15, 2026
  20. Jackery Explorer 1000 v2 product page — checked October 15, 2026
  21. Jackery Explorer 1000 Plus product page — checked October 15, 2026
  22. Jackery Explorer 2000 v2 product page — checked October 15, 2026
  23. Jackery Explorer 5000 Plus product page — checked October 15, 2026
  24. Anker SOLIX C1000 Gen 2 product page — checked October 26, 2026
  25. Anker SOLIX C2000 Gen 2 product page — checked October 26, 2026
  26. Anker SOLIX F3000 product page — checked October 26, 2026
  27. Anker SOLIX F3800 Plus product page — checked October 26, 2026
  28. Bluetti AC180 product page — checked October 26, 2026
  29. Bluetti Elite 100 V2 product page — checked October 26, 2026
  30. Bluetti Elite 200 V2 product page — checked October 26, 2026
  31. Bluetti Elite 30 V2 product page — checked October 26, 2026
  32. Bluetti Elite 300 product page — checked October 26, 2026
  33. Bluetti Elite 400 product page — checked October 26, 2026
  34. Bluetti AC200L product page — checked October 26, 2026
  35. Bluetti Apex 300 product page — checked October 26, 2026
  36. DJI Power 1000 V2 product page — checked October 15, 2026
  37. EcoFlow DELTA Pro Ultra product page — checked October 15, 2026

Keep going

Photo: Devon MacKay on Unsplash (Unsplash License).