What size power station do I need?
Short answer: add up the watt-hours your devices use in a day, then divide by about 0.85 to cover inverter losses. Keeping a full-size fridge, Wi-Fi, phones and a few LED lights running for one day takes about 2,100 Wh. The power station also needs enough surge watts to start the fridge compressor.
1. What do you want to keep running?
Watts are typical values. For the exact number, check the label on the device or its manual. Hours means hours the device actually draws power in a day.
2. What you need
- Battery capacity
- 2,065 Wh
- Continuous output
- 300 W
- Surge output
- 1,239 W
Look for 3,000 Wh or more.
Everything on your list at once is 189 W. This adds 20% headroom.
Running load plus the biggest start-up jump (1,050 W).
A 1,000 Wh unit runs this list for about 12 hours.
How this is calculated
- Daily energy = sum of (running watts × hours per day × quantity) = 1,755 Wh.
- Battery capacity = daily energy × days ÷ usable share (85%). Part of every battery's rated capacity is lost in the inverter that turns battery power into wall-outlet power.
- Continuous output = everything running at once × 1.2, rounded up to the next 100 W.
- Surge output assumes motors (fridge, pumps, furnace fan) start one at a time, so only the largest start-up jump is added.
The three numbers on every power station
Spec sheets list three ratings. Each one answers a different question.
- Capacity (Wh) is how much energy the battery stores. It decides how long your devices run.
- Continuous output (W) is how much power it can deliver at the same moment. It decides how many devices can run together.
- Surge output (W) is the short burst it can give for a second or two. Motors in fridges, pumps and furnace fans need this burst to start.
A unit can have plenty of capacity and still fail to start your fridge if its surge rating is too low. Check all three.
A worked example
Here is the default list in the calculator above, for one day:
| Device | Watts | Hours/day | Wh/day |
|---|---|---|---|
| Refrigerator | 150 | 8 | 1,200 |
| Wi-Fi router and modem | 20 | 24 | 480 |
| Phone charging | 10 | 3 | 30 |
| LED light bulb | 9 | 5 | 45 |
| Total | 1,755 |
1,755 Wh ÷ 0.85 = about 2,065 Wh. A 2,000 Wh unit comes up just short for a full day, so a 3,000 Wh unit, or a 2,000 Wh unit plus some solar charging, is the safer pick.
The fridge is rated for 8 hours a day, not 24, because its compressor switches on and off. A typical modern full-size fridge uses roughly 1 to 2 kWh a day. Your fridge's yellow EnergyGuide label lists its yearly kWh. Divide that by 365 for a daily figure.
How long common sizes last
Estimated runtime, assuming 85% of the rated capacity reaches your devices:
| Capacity | Fridge only (1,200 Wh/day) | Fridge, Wi-Fi, phones, lights (1,755 Wh/day) |
|---|---|---|
| 500 Wh | about 8.5 hours | about 6 hours |
| 1,000 Wh | about 17 hours | about 12 hours |
| 2,000 Wh | about 34 hours | about 23 hours |
| 3,000 Wh | about 51 hours | about 35 hours |
What a power station is not good for
Anything that makes heat drains a battery fast. A 1,500 W space heater uses about 1,500 Wh every hour it runs. Electric stoves, water heaters, electric furnaces and central AC need far more power than a portable unit can give. For those, a generator or a whole-home battery system installed by an electrician is the realistic option.
Never connect a power station or generator to your home's wiring through an outlet. Use extension cords to the devices, or have an electrician install a transfer switch.
Common questions
Can a 1,000 Wh power station run a refrigerator?
Yes, for about 17 hours if the fridge uses 1,200 Wh a day, as long as the unit's surge rating can start the compressor. A fridge compressor can need well over 1,000 W for a moment at start-up.
Why does my power station show less energy than its rating?
The rating is the battery's stored energy. Converting it to 120 V AC power loses some of it as heat, usually 10 to 15%. Charging phones and laptops from the USB-C ports skips that conversion and wastes less.
Is a power station or a generator better for outages?
A power station is quiet, safe indoors and needs no fuel, but it holds a fixed amount of energy. A generator runs as long as you have fuel and powers bigger loads, but it must run outdoors, far from windows, because of carbon monoxide.
Sources
- Home Depot: Choosing the right size generator(motor starting watts are often about three times running watts)
- Device watts in the calculator are typical values. Your device's label or manual has the exact figure.