Power Station Sizing Calculator
Start from what you need to run and for how long, and get a watt-hour target to shop with. The result builds in conversion losses and a planning reserve, so you can pick a size with confidence instead of guessing between models.
Size your power station
Results update as you type. Every assumption is adjustable.
Recommended size
627 Wh
To run your device at 60W for 8 hours (8 hr), shop for stations rated around this figure or higher.
Minimum energy needed
565 Wh
Delivered energy needed with conversion losses counted, before the 10% planning reserve is added.
Capacity class
500–1,000Wh
What this class typically looks like: toolbox-size stations that can run several devices at once for a day or more.
Next steps
How this is calculated
Both figures come from the sizing formula in our shared calculation library:
requiredWh = (deviceWatts * desiredHours) / (efficiency / 100) recommendedWh = requiredWh / (1 - reserve / 100) In plain English: first we work out the energy your device consumes over the target window — watts times hours. Dividing by the efficiency percentage grosses that up for conversion losses, because a battery must store more than the device consumes; the inverter takes its share. That gives the minimum. Dividing again by one-minus-reserve adds a planning buffer, producing the recommended size we suggest shopping with.
Default assumptions
- 85% efficiency — a typical figure for AC output through an inverter. Direct USB-C or 12V DC output loses less; 90–95% is fair there.
- 10% reserve — headroom for battery aging, cold weather, and estimate error, so the recommendation survives contact with reality.
- Steady draw — we assume the wattage you enter is a continuous average. Devices that cycle on and off, like fridges, average lower than their running watts.
The full method — and why we picked these defaults — is on How we estimate.
What to do with this number
Some links on this page may be paid links. If you buy through them, Cynosure LLC may earn a commission at no extra cost to you. We do not claim to have personally tested products unless clearly stated.
Example power stations by capacity class
Once you have a watt-hour target, these placeholder examples show what each class typically offers in output, weight, and price. Specs are illustrative category estimates, not specific models.
Some links on this page may be paid links. If you buy through them, Cynosure LLC may earn a commission at no extra cost to you. We do not claim to have personally tested products unless clearly stated.
| Product | Capacity | Output | Ports | Weight | Est. price | Ideal for | Link |
|---|---|---|---|---|---|---|---|
| Example 300Wh Power Station Placeholder Brand | 300Wh | 300W AC | AC ×1, USB-C 100W, USB-A ×2, 12V car port | 7–10 lb | $150–$250 | Router and modem backup, Charging phones and tablets for days, A laptop for a few hours, Car trips and short outages | Link pending |
| Example 500Wh Power Station Placeholder Brand | 500Wh | 500W AC | AC ×2, USB-C 100W, USB-A ×2, 12V car port | 13–17 lb | $250–$450 | A full laptop workday, A day or more of router and modem backup, Weekend camping electronics, Fans, lights, and small electronics together | Link pending |
| Example 1,000Wh Power Station Placeholder Brand | 1,000Wh | 1,000W AC | AC ×3, USB-C 100W, USB-A ×2, 12V car port, DC5521 ×2 | 22–28 lb | $500–$900 | Multi-day phone and internet backup, A mini fridge through an outage, Family camping trips, Several devices running at once | Link pending |
| Example 2,000Wh Power Station Placeholder Brand | 2,000Wh | 2,000W AC | AC ×4, USB-C 100W ×2, USB-A ×2, 12V car port, DC5521 ×2 | 45–60 lb | $1,000–$1,900 | Days of essentials during long outages, A full-size refrigerator in duty cycles, High-draw devices up to 2,000W, Base camp or supplemental RV power | Link pending |
Placeholder examples with category-typical specs, not specific tested products. Verify capacity, continuous output, and surge ratings on the manufacturer’s spec sheet.
Frequently asked questions
Should I buy the minimum size or the recommended size?
Buy at or above the recommended number. The minimum is the bare energy your device needs with conversion losses counted; it leaves no margin for estimate error, battery aging, or the extra device you did not plan for. The recommended figure adds a reserve so the plan still works when reality runs a little worse than the math.
How do I size for several devices at once?
Add the running watts of everything you want powered at the same time and enter the total. Two things then need to check out: the battery needs enough watt-hours for the combined load over your target hours, and the station’s continuous AC output rating must be higher than the combined draw at any single moment.
What is the difference between watts and watt-hours?
Watts measure how fast a device uses energy; watt-hours measure how much energy a battery stores. A 60W laptop running for 8 hours consumes about 480 watt-hours before losses — which is why it needs a bigger battery than the wattage alone suggests. Our watt-hours vs. watts guide walks through it with examples.
Do surge loads change what size I need?
Surge changes which station you can use more than how many watt-hours you need. Devices with compressors or motors — refrigerators are the classic case — briefly draw far more than their running watts at startup. Your watt-hour math stays the same, but the station’s surge rating must cover that startup peak, so check it on the spec sheet.
Calculations are estimates only. Real runtime depends on battery age, inverter efficiency, device behavior, temperature, surge loads, manufacturer limits, and actual measured wattage. Always verify product specifications before buying or relying on a setup.
Affiliate disclosure
Some links on this page may be paid links. If you buy through them, Cynosure LLC may earn a commission at no extra cost to you. We do not claim to have personally tested products unless clearly stated.