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The single most common question when shopping for a backup power station is: how big do I actually need? Buy too small and it won’t cover what matters during an outage; buy too big and you’ve overspent. Here’s how to size it correctly.
Step 1: List What You Actually Need to Power
Most households don’t need to power everything during an outage — just the essentials. Typical running (not starting) wattage for common devices:
| Device | Typical Running Watts | Typical Starting/Surge Watts |
|---|---|---|
| Full-size refrigerator | 100-250W | 600-1,500W |
| WiFi router/modem | 10-20W | — |
| CPAP machine (no heated humidifier) | 30-60W | — |
| CPAP machine (with heated humidifier) | 60-90W | — |
| LED lighting (per bulb) | 5-15W | — |
| Laptop | 30-65W | — |
Note the difference between running watts (what a device draws once it’s operating) and starting/surge watts (the brief spike many motor-driven appliances, especially refrigerators, need to start up — often 3-5x the running wattage). Your power station’s continuous output rating needs to cover your total running watts, and its surge rating needs to cover the highest single starting-watt spike you’ll hit.
Step 2: Estimate Your Watt-Hour Need
Watt-hours (Wh) measure total energy storage — how long you can run your devices before recharging. A rough formula: (total running watts) × (hours you need backup) = watt-hours needed. For example, a refrigerator averaging 150W running continuously for 8 hours needs roughly 1,200Wh just for the fridge (refrigerators cycle on and off, so real-world draw is often lower than this worst-case estimate, but it’s a safer starting point).
As a practical reference point, see how this plays out with real products in our best portable power stations roundup: a 268Wh unit like the Bluetti EB3A suits phone/router/CPAP-only backup, while a 1,000Wh+ unit like the Jackery Explorer 1000 v2 is sized more for refrigerator-inclusive backup.
Step 3: Decide Between a Power Station and a Fuel Generator
Battery power stations are quiet, produce no exhaust, and can be used indoors, but they have a fixed energy budget until recharged (via wall outlet, car, or solar). Fuel generators can run indefinitely as long as you have fuel, but they’re loud, require outdoor placement, and carry a serious carbon monoxide risk. See our full breakdown: Solar Generator vs. Gas Generator: Which Should You Buy?
Safety Guidance for Fuel-Powered Generators
If you use or are considering a fuel-powered (gas/propane/dual-fuel) generator, the U.S. Consumer Product Safety Commission (CPSC) guidance is unambiguous and life-safety critical:
- Never operate a portable generator indoors — not in a home, garage, basement, crawlspace, or shed — even with doors and windows open. Generator exhaust contains carbon monoxide, an odorless, invisible gas that can be lethal within minutes.
- Operate generators outdoors only, at least 20 feet away from your home, with the exhaust directed away from windows, doors, and vents.
- Install carbon monoxide detectors in your home and test them regularly, particularly if you use a fuel generator during outages.
- Always read the specific generator’s manual for model-specific safety instructions before first use.
Source: U.S. Consumer Product Safety Commission, Carbon Monoxide Information Center. Battery-based power stations do not produce exhaust and do not carry this specific risk, which is one reason many households choose them as a primary or supplemental backup option.
Quick Sizing Recommendations
| Use Case | Recommended Capacity |
|---|---|
| Phones, router, small electronics only | 200-300Wh |
| Above + CPAP machine overnight | 300-700Wh |
| Above + refrigerator for several hours | 1,000Wh+ |
| Multi-day whole-home essentials backup | 2,000Wh+ or consider a backup generator |
Ready to see specific options at each tier? Check our best portable power stations for home backup roundup and our best solar generators under $1,000 guide.