What size power station do you need?
Start from your devices, not from watts you don't know. We do the honest math — real usable capacity, startup surge, solar recharge reality — and answer with stations at live, timestamped prices.
1 · What are you preparing for?
- Devices need (per day)
- 720Wh
- Running load
- 100W
- Startup surge peak
- 700W
A 1,000Wh-class station covers your 1-day need — startup surge, not running watts, is what rules out smaller units here.
- You need (battery side)
- 847Wh battery-side
- Running load
- 100W
- Startup surge peak
- 700W
How we got there
| Device | Avg draw | Over 1 day |
|---|---|---|
| Chest freezer | 30W | 720Wh |
| Devices total | 720Wh |
On top of the device total, each station is charged its real conversion losses — AC loads ÷ inverter efficiency (0.85 typical, by chemistry), DC loads ÷ 0.9 — and capacity is counted from the best number we have for that unit: lab-measured usable, else the manufacturer's usable figure, else rated × 0.9 depth-of-discharge. No vague “reserve” padding — every derate is named in the methodology.
Smallest station that passes everything — we don’t oversell.
- Runs your kit
- 1.2 days
- AC delivered
860 Whverified. Show source
verified sourceindependently measured AC-delivered capacity- Weight
- 12.9 kg
- capacity fits
- inverter handles the load
- starts your compressors
☀️ With your panels this still loses 287Wh/day — dead in ~3.5 days. Indefinite runtime needs ~350W of panels.
Cheapest passing station at a genuinely good price today.
- Runs your kit
- 1.3 days
- AC delivered
950 Whverified. Show source
verified sourceindependently measured AC-delivered capacity- Weight
- 16 kg
- capacity fits
- inverter handles the load
- starts your compressors
☀️ With your panels this still loses 287Wh/day — dead in ~3.9 days. Indefinite runtime needs ~350W of panels.
One size up, for when it runs longer than planned.
- Runs your kit
- 1.8 days
- AC delivered (est.)
1,279 Whest.. Show source
estimated sourcebattery-side capacity × published AC-efficiency constant- Extra vs right-size
- +0.6 days
- Weight
- 23.9 kg
- capacity fits
- inverter handles the load
- starts your compressors
☀️ With your panels this still loses 287Wh/day — dead in ~5.2 days. Indefinite runtime needs ~350W of panels.
Scenario: Custom kit — 1 days Duration: 1-day Energy need (battery side): 847Wh usable Running load: 100W Peak startup surge: 700W Recommended minimum: 1,000Wh class, Why: startup surge, not running watts, is what rules out smaller units here.
Real examples
Can a 1,000Wh power station run a refrigerator through a 2-day outage?
Usually not: a full-size fridge averages ~1.26kWh/day at the wall, so two days needs ~3kWh of usable battery once inverter losses are counted — plus a ~900W startup surge the inverter must clear.
Run this exact setup →How big a battery do 3 nights of CPAP need?
With the humidifier off and a DC adapter, ~9W × 8h is only ~80Wh a night — a few hundred watt-hours covers a long weekend. Heated humidification multiplies that by 5–6×.
Run this exact setup →What runs a weekend camp with a 12V fridge and Starlink?
The fridge sips (~320Wh/day on DC) but Starlink is the quiet hog — ~1.8kWh/day if it stays on. Check the solar answer: most 100W panels can't keep up with that.
Run this exact setup →How the math works
Every constant is published — same numbers as our scoring methodology, no house secrets:
- Device energy: nameplate watts × duty cycle (compressors cycle; a fridge's average is far below its label) × hours × days. Your watt-meter measurement overrides ours.
- Capacity truth: lab-measured usable Wh when we have it → manufacturer usable figure → rated × 0.9 depth-of-discharge default. Never double-derated.
- Conversion losses: AC loads ÷ 0.85 inverter efficiency (chemistry-specific where known); DC loads ÷ 0.9.
- Surge check: largest single startup surge + everything else still running, vs the station's sourced surge rating. No sourced rating → flagged “unverified”, never guessed.
- Solar reality: harvest = min(your panels, station's max input) × 4 peak-sun hours × 0.7 real-world derate.
- Right-size pick: smallest passing station with 15–30% capacity headroom — we don't oversell, and the Value pick only appears when a passing station is at a genuinely good tracked price.
Sizing questions, straight answers
Watts vs watt-hours — what's the difference?
Watts (W) are a rate — how hard your devices pull right now. Watt-hours (Wh) are a quantity — how much energy the battery holds. A 300W load drains 300Wh every hour. You need both: enough watts (inverter) to run everything at once, and enough watt-hours (capacity) to run it for as long as you need.
Why do you count less than the rated capacity?
No station delivers its label. The battery holds back a protection reserve, and the inverter loses ~15% turning DC into AC. Where a unit has been lab-measured we use that number; otherwise the manufacturer's usable figure; otherwise rated × 0.9 — and then AC loads still pay the inverter toll. That's why a "1,000Wh" unit realistically serves ~765Wh of AC.
What are starting (surge) watts and why do they matter?
Motors and compressors briefly pull 2–6× their running watts at startup. A fridge that runs at 180W can spike past 1,000W for a moment — and if the station's surge rating can't clear it, the unit trips even though the math "fit". We check the worst single-start moment against each station's sourced surge spec.
Can solar keep a power station running forever?
Only if daily harvest beats daily draw. We assume 4 peak-sun hours and real-world panel losses (×0.7), capped by what the station's charge controller physically accepts. The calculator tells you the panel wattage indefinite runtime actually requires — and flags when a station can't accept that much.