How to Size a Portable Power Station: Wh Math That Actually Works
The single most common mistake buyers make is sizing a portable power station by its wattage instead of its capacity. Watts tell you how fast a device can pull power; watt-hours (Wh) tell you how long you can run it. Get the Wh right and the station just works. Get it wrong and your fridge dies at 2 a.m.
1. The only formula you need
Runtime (hours) ≈ Station Wh ÷ Device watts × 0.85 (the 0.85 covers inverter loss). A 500Wh station runs a 50W laptop about 8.5 hours. It cannot run a 1,500W space heater for long no matter how "powerful" the box looks.
2. Build your device list
| Device | Draw | Daily need |
|---|---|---|
| Smartphone | 10W | ~20Wh |
| Laptop | 60W | ~300Wh |
| LED camp lights | 10W | ~60Wh |
| 12V fridge | 40W avg | ~500–900Wh |
| Wi-Fi router | 10W | ~240Wh |
| Full-size fridge | 150W avg | ~1,500–2,000Wh |
Add a 15% buffer, then round up. That final number is your minimum Wh.
3. Three worked examples
Weekend camping (~800Wh/day)
Phone, lights, a drone, a small fan. The RIVER 3 Plus (858Wh) covers it and still charges from your car on the drive up.
Family basecamp (~1,500Wh/day)
Fridge, laptops, projector. The DELTA 3 (1,024Wh, expandable) or DELTA 3 Plus handles a full weekend and tops up on a 220W panel.
Home backup fridge (~2,000Wh/day)
A full-size fridge through an outage needs the DELTA Pro 3 (3,000Wh+, expandable to 48kWh). See our Home Backup Power 101 for the full runtime math.
4. Don't forget surge
Fridge compressors and power tools spike 2–3× their running watts on startup. Confirm your station's surge rating covers the brief spike, or it will trip offline.
5. FAQ — sizing
Should I buy exactly my minimum Wh?
No. Buy 1.5–2× your daily need so you're not at 0% every evening, and leave room to grow with extra batteries.
What if my needs change?
Choose a model with extra-battery support—like the DELTA line—rather than buying twice. Expansion beats replacement.
Why buy from Livvoltpower?
We're an authorized EcoFlow dealer. Every unit ships with the full manufacturer warranty, a 5-year battery warranty, and US-based support—plus bundle pricing you won't find on marketplaces.
Shop Power Stations →Livvoltpower is an authorized EcoFlow dealer. Specs reflect manufacturer data; pricing and availability subject to change.