Disclosure: our picks are independent. Some links are affiliate links (we may earn a commission at no cost to you). How we choose
Contents
Quick answer
Phones, laptop, lights, Wi-Fi, CPAP: 300 to 500 WhA small unit like the EcoFlow RIVER 3 Plus covers a night or two. Check price
Fridge plus essentials for a day: about 1,000 to 2,000 WhThe Anker SOLIX C1000 Gen 2 is our pick at 1 kWh. Check price
Sump or well pump, multi-day outages: 4,000 Wh and upLook at whole-home units like the EcoFlow DELTA Pro 3. Check price
Power station sizes are given in watt-hours (Wh): the amount of energy stored. The other key number is the inverter output in watts (W): how much power it can deliver at once. You need both to be large enough.
The formula
Watt-hours needed = appliance watts × hours of use, then add about 15 % for inverter losses. For several appliances, add up the results.
Example: a 60 W CPAP for 8 hours = 480 Wh, plus 15 % ≈ 550 Wh. A 500 Wh unit would be just short; choose the next size up.
Video: “What Size Power Station Do You REALLY Need?” by CleverJoe Off Grid (YouTube). Not affiliated with Grid Out Ready.
Typical appliance consumption
| Appliance | Typical running watts | Energy per day or use |
|---|---|---|
| Phone charge | 10–20 W | ~15 Wh per charge |
| Laptop | 40–90 W | ~60 Wh per hour |
| Wi-Fi router + modem | 15–30 W | ~500 Wh per day |
| LED light bulb | 8–10 W | ~50 Wh per evening |
| CPAP (no humidifier) | 30–60 W | ~400 Wh per night |
| Full-size fridge | 100–200 W (surge higher) | ~1,000–2,000 Wh per day |
| Sump pump (1/3 hp) | ~800 W (surge higher) | Depends on cycles |
| Microwave | 1,000–1,500 W | ~100 Wh per 5 minutes |
| Space heater | 1,500 W | 1,500 Wh per hour |
These are typical ranges: check the label on your own appliances, or use a plug-in watt meter for the most accurate numbers.
Which size should you buy?
Under 500 Wh: devices and medical equipment
Enough for phones, laptops, lights, the router and a CPAP for a night. Light, affordable and ideal for camping. Not for appliances.
1,000 to 2,000 Wh: the sweet spot for most homes
Keeps the fridge cold through a typical outage while charging devices and running lights. See our picks for the best portable power stations.
4,000 Wh and up: real home backup
Needed for sump or well pumps, multi-day outages or 240V appliances, ideally connected through a transfer switch. See the best power stations for home backup.
Method: appliance figures are typical ranges from manufacturer labels and energy-efficiency data; your appliances may differ.