What needs to stay on when the power goes out?

A storm warning just hit. You have minutes to decide what backup battery keeps your phone, CPAP, or fridge running β€” without overspending.

Select devices and hours offline
Phone
~18 W
Laptop
~65 W
Router
~10 W
CPAP
~60 W
Fridge
~200 W

Honest Math, No Upsell

Every number below is derived from the same transparent formula. No hidden multipliers, no brand bias.

Formula

Wh = Ξ£(W Γ— h) Γ— 1.2

Sum of (device wattage Γ— hours needed) with a 20% safety margin for inverter loss, battery aging, and temperature.

Embedded device wattages

  • Phone: 5–30 W (charging)
  • Laptop: 30–100 W (charging + use)
  • Router: 5–15 W
  • CPAP: 30–90 W (varies by pressure/humidifier)
  • Fridge: 100–800 W (surge on compressor start)

Values are midpoints of typical ranges. Your actual device may vary β€” check its label.

Category tiers (early-2024 retail snapshot)

  • Power Bank β€” <100 Wh
  • UPS β€” 100–500 Wh
  • Power Station β€” 500–2,000 Wh
  • Solar Generator β€” >2,000 Wh

Tiers are static retail categories, not live prices or specific model recommendations.

20%
Safety Margin Applied
Formula: Wh = Ξ£(W Γ— h) Γ— 1.2

Reuse whenever life changes β€” new device, parent's medical gear, camping prep, RV build, next storm season.

Watt Cart β€” Neutral backup power sizing. No brand upsell, ever.