Calculate Wh needs, then pick a station class

Enter watts × hours, or average Wh/day for cycling loads. The calculator returns nameplate Wh. Units under the result are specific stations in that class, not a ranked review. Amazon Associates is live; EcoFlow / Jackery / Bluetti partner links are not.

AC path nameplate: Wh per day times days, divided by inverter efficiency 0.90, times 1.15 buffer, divided by depth of discharge 0.90. Do not apply 0.90 to a 12 V DC fridge. Set efficiency to 1.00 on that path. — EXAMPLE. AC-path defaults (η=0.90, DoD=0.90, buffer=0.15). 12 V DC fridge: set η = 1.00. Camping-sample fridge 320 Wh/day is a planning band, not the CFX3 35 282 Wh/day test point. See how it works.

WattNeeds defaults: inverter efficiency η=0.90, DoD=0.90, buffer=0.15. One-liner: nameplateWh = (whPerDay × days × 1.15) / (0.90 × 0.90). Always re-check continuous watts and surge against the station inverter.

Disclaimer: Estimates only — not professional electrical advice and not medical advice (including CPAP). Verify continuous watts, surge, and usable Wh against manufacturer specs before you buy or rely on a station for critical loads.

Devices

Enter either Watts + hours/day or Wh/day (leave watts/hours blank if using Wh/day). Fridges: average Wh/day, not compressor W × 24. 12V DC fridge: set inverter efficiency to 1.00 — default 0.90 is the AC path. Camping-sample fridge 320 Wh/day is a planning band, not the CFX3 35 282 Wh/day manufacturer test point.

Autonomy & losses

Days of autonomy

Inverter efficiency (0.85–0.95)

Usable DoD (0.80–0.95)

Planning buffer (0–0.30)

Optional runtime check

Candidate nameplate Wh

Recommended usable Wh (battery-side with buffer)

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Recommended nameplate Wh

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How the math works →

Example sizing for a 12-hour outage: mini fridge 40 watts times 12 hours is 480 Wh, laptop 180 Wh, LED 50 Wh, phone 20 Wh, total 730 Wh. A 15 percent buffer makes 839.5 Wh. Divided by 0.90 depth of discharge and 0.90 inverter efficiency, the AC nameplate is about 1,036 Wh, which fits the about 1,000 Wh class (results 513 to 1,152). Compare that result to the station label. All 12 V DC devices would be about 933 Wh. The fridge 40 W is an average because the compressor cycles. — EXAMPLE device list, not your calculator result. Your result appears above. 480 + 180 + 50 + 20 = 730 Wh. 730 × 1.15 = 839.5. 839.5 / 0.90 / 0.90 = 1,036.42, shown as ~1,036 Wh. 12 V DC skips the inverter: 839.5 / 0.90 = 932.78, shown as ~933 Wh. Fridge 40 W is an average over the window.

Example: a 1,000 Wh station label times 0.90 inverter efficiency times 0.90 depth of discharge equals 810 Wh usable on AC. A continuous 100 W AC load runs 8.1 hours, about 8 hours. Plan on about 81 percent of the label for AC. — EXAMPLE. 1,000 × 0.90 × 0.90 = 810 Wh usable AC. 810 / 100 W = 8.1 hours. Plan on ~81% of the label for AC.

Next: sizing guides · Wh tiers · formula

Quick links

Camping fridge Wh needs — average daily energy, not nameplate watts
CPAP overnight sizing — estimates + safety notes
Home outage essentials — router, lights, fridge, phones
Van-life daily Wh budget — fridge + lights baseline
EcoFlow vs Jackery vs Bluetti — how to compare (no fake rankings)

Where to check pricing

As an Amazon Associate, we earn from qualifying purchases at no extra cost to you. EcoFlow, Jackery, and Bluetti partner programs are not live yet.

See on Amazon EcoFlow — Coming soon Jackery — Coming soon Bluetti — Coming soon