BackupPowerAI · Sizing calculator · Rev. Oct 2026
How many watt-hours does your outage need?
Tick the loads that must stay on. The table multiplies watts by hours, applies the fridge duty cycle, then sizes the battery for inverter loss and headroom. The full quiz shows every step of the math.
Live sizing table
Tick a row to add it
| On | Appliance | W × h | Wh/day |
|---|---|---|---|
| 200×24 | 1,600 | ||
| 150×24 | 0 | ||
| 60×8 | 480 | ||
| 20×24 | 480 | ||
| 40×5 | 200 | ||
| 50×3 | 150 | ||
| 800×2 | 0 | ||
| 600×8 | 0 | ||
| Total per day | 2,910 |
- Battery, 3 days
- 12,325Wh
- Surge needed
- 1,370W
Battery = 2,910 Wh × 3 ÷ 0.85 inverter × 1.2 headroom. Typical watts from published charts. Use your own labels in the quiz.
Section 01
Outage figures, with sources
11h
Average total interruption per U.S. customer in 2024. The most in 10 years, driven mostly by hurricanes.
Source: EIA, Dec 2025+20GW
Year-over-year rise in winter peak demand. NERC warns that wide-area extreme cold could cause supply shortfalls.
Source: NERC, Nov 20254.4%
Share of U.S. electricity used by data centers in 2023, projected at 6.7 to 12% by 2028.
Source: DOE/LBNL, Dec 20244h
How long refrigerated food stays safe with the door shut. A full freezer holds about 48 hours.
Source: CDC, Nov 2025Section 02
One pick per power type
Research-based picks from manufacturer specs and published data. We don't test products. For the tradeoffs between types, read power station vs. generator.
DisclosureAs an Amazon Associate we earn from qualifying purchases. We may earn a commission when you buy through links on this site, at no extra cost to you. Learn more.
Spec sheet: research-based picks
- Power stationJackery Explorer 1000 v2
A fridge, router and lights through a typical outage. Runs indoors with no noise.
- Capacity
- 1,070 Wh
- Cont./surge
- 1,500 / 3,000 W
- Chem./fuel
- LiFePO4
- Weight
- 23.8 lb
- Solar kitJackery Solar Generator 1000 v2 + 200W
Recharging essentials day after day without storing fuel.
- Capacity
- 1,070 Wh
- Cont./surge
- 1,500 / 3,000 W
- Chem./fuel
- LiFePO4 + 200 W solar
- Weight
- 23.8 lb (station)
- Dual-fuel generatorChampion 3500W Dual Fuel (201296)
Multi-day outages with a fridge, freezer and sump pump. Outdoors only.
- Capacity
- Fuel, 4.7 gal tank
- Cont./surge
- 3,500 / 4,375 W gas3,150 / 3,950 W LP
- Chem./fuel
- Gasoline + Propane
- Weight
- 104.7 lb
Specs from each manufacturer's page, checked Oct 27, 2026. Solar kit weight is the station alone.
Section 03
The sizing method
The calculator uses six formulas and five constants. Typical watts come from Champion's wattage chart and the DOE appliance list. Your appliance label beats both, so the quiz lets you overwrite every value.
The 0.85 inverter figure is the conservative end of a DOE-submitted Florida Solar Energy Center report, which models 0.84 to 0.93 depending on load. The 1.2 headroom keeps you from planning to run the battery to zero.
| No. | Output | Formula |
|---|---|---|
| 01 | Daily energy | W × qty × h/day × duty cycle, summed |
| 02 | Battery, 1 day | daily Wh ÷ 0.85 × 1.2 |
| 03 | Battery, outage | battery 1 day × days, no recharging |
| 04 | Continuous rating | sum of running W × 1.2, rounded up to 100 W |
| 05 | Surge rating | running W + largest single motor start |
| 06 | Solar to refill | daily Wh ÷ 0.85 ÷ (4 sun-h × 0.75) |
Section 04
Guides
- 01Best Portable Power Stations for Power Outages (2026)Six LiFePO4 picks from phone-and-CPAP size to whole-home scale, with runtime math for each.Buying guide
- 02Best Dual-Fuel Generators for Home Backup (2026)Five gasoline + propane picks with CO shutoff, from fridge-and-sump size to 240 V transfer-switch size.Buying guide
- 03Best Solar Generator Kits for Long Power Outages (2026)Power station + panel bundles that recharge without fuel, with the math on how much sun you really need.Buying guide
- 04Power Station vs. Generator: Runtime, Watts, Safety and Cost ComparedSide-by-side comparison of batteries and fuel generators, and why many homes end up with both.Buying guide
- 05What Size Power Station You Need: The Sizing Math, Worked ThroughFour-step sizing math with worked examples. It is the same method our quiz uses.Sizing
- 06How to Power a Refrigerator During a Power OutageFood-safety clock, fridge watts and the battery or generator size that keeps it cold.How-to
- 07CPAP Backup Power: How to Keep Your CPAP Running in an OutageCPAP watts, humidifier impact, DC adapters and battery sizes for one to several nights.How-to
- 08Generator Safety: How to Prevent Carbon Monoxide PoisoningThe CDC and CPSC rules: placement, CO alarms, backfeeding, fuel and symptoms to know.Safety
- 09Transfer Switch and Interlock Basics for Backup PowerHow a generator or big power station safely feeds home circuits, and what to ask your electrician.How-to
Section 05
Questions about the calculator
- How does BackupPowerAI size my backup power?
- You pick the appliances you need and how long the outage lasts. We multiply watts × hours (with a duty cycle for fridges and freezers), divide by 0.85 for inverter losses, add 20% headroom, and add the largest motor's start-up surge. Every step is shown on your results page.
- Is it free? Do I have to give my email?
- It's free and your results appear instantly with no email. Installer matching for whole-home systems opens in early 2027; you can leave your email and ZIP to hear when it does.
- How accurate is it?
- It's a planning estimate built on typical wattages from published charts. You can replace any typical value with the watts on your own appliance label, which makes it much more accurate. Real-world draw varies with model, age and temperature.
- Do you test the products you recommend?
- No. Our picks are research-based, built from manufacturer specs and published data. We link each manufacturer's page so you can confirm the specs.
- How do you make money?
- We earn commissions from qualifying Amazon purchases through our links, at no extra cost to you, and may be compensated for installer referrals. That never changes the sizing math.