What Size Portable Power Station Do I Need? Wh, Watts & Solar
Portable power stations are big batteries with a built-in inverter. They are quiet, need no fuel, and can be recharged from the wall, the car or solar panels. The key to choosing one is two numbers: watt-hours (Wh), which says how long it will run, and watts (W), which says what it can run at the same time. A fridge, router, lights and phones for one day needs roughly 2,500 to 3,000 Wh. A CPAP machine overnight needs only about 400 Wh.
Wh vs W: the two numbers that matter
- Capacity in watt-hours (Wh) is the size of the "fuel tank". A 1,000 Wh station can deliver 1,000 watts for one hour, or 100 watts for 10 hours.
- Output in watts (W) is how fast it can deliver power. A station with a 300 W inverter cannot run a 700 W appliance, however big its battery.
- Surge rating is the brief higher output the inverter can supply for a second or two, which motors and compressors need to start.
How to work out the size you need
- List the devices you want to power, with their watts and the hours a day you will use each.
- Multiply watts by hours for each, and add up the watt-hours per day.
- Add 15% for losses in the inverter and battery (divide by 0.85), and multiply by the number of days you want to run without recharging.
- Check the output. Add up the watts of the devices that will run at the same time, and make sure the inverter (and its surge rating) covers that.
The power station size calculator does this from a list of common devices, and also works out the solar panels to recharge it.
Examples
| What you power | Energy per day | Battery needed | Size to shop for | Output at once |
|---|---|---|---|---|
| Overnight CPAP (8 hours) | 320 Wh | 376 Wh | 500 Wh or more | 60 W |
| Phones, laptop, router and lights for a day | 895 Wh | 1,053 Wh | 1,500 Wh or more | 175 W |
| Camping weekend day: mini fridge, lights, fan, phones | 1,415 Wh | 1,665 Wh | 2,000 Wh or more | 245 W |
| Working from home: laptop, router, lights (8 hours) | 1,000 Wh | 1,176 Wh | 1,500 Wh or more | 155 W |
| Fridge, router, lights, phones, laptop (one day) | 2,335 Wh | 2,747 Wh | 3,000 Wh or more | 875 W |
| The above for 2 days | 2,335 Wh | 5,494 Wh | 6,000 Wh or more | 875 W |
| The above + TV (3 h) + microwave (15 min) | 2,885 Wh | 3,394 Wh | 4,000 Wh or more | 2,025 W |
The refrigerator is the big one: even an efficient fridge uses more than 1,000 Wh over a day, so it dominates the budget. Anything that makes heat (a microwave, kettle, heater or hair dryer) draws 1,000 W or more, which empties a small station in well under an hour.
How long will it run?
Usable energy is roughly 85% of the label. Divide it by the load in watts to get the hours. For a 1,000 Wh station: 850 Wh ÷ 100 W = 8.5 hours. Use the runtime calculator for any capacity, or for a battery rated in amp-hours (multiply Ah by volts to get Wh).
| Load | 300 Wh | 500 Wh | 1,000 Wh | 2,000 Wh | 3,000 Wh |
|---|---|---|---|---|---|
| 25 W | 10.2 h | 17.0 h | 34.0 h | 68.0 h | 102.0 h |
| 50 W | 5.1 h | 8.5 h | 17.0 h | 34.0 h | 51.0 h |
| 100 W | 2.5 h | 4.3 h | 8.5 h | 17.0 h | 25.5 h |
| 200 W | 1.3 h | 2.1 h | 4.3 h | 8.5 h | 12.8 h |
| 500 W | 0.5 h | 0.8 h | 1.7 h | 3.4 h | 5.1 h |
| 1,000 W | 0.3 h | 0.4 h | 0.8 h | 1.7 h | 2.5 h |
| 1,500 W | 0.2 h | 0.3 h | 0.6 h | 1.1 h | 1.7 h |
What common devices use
Typical figures. Check the label on your own device, or use a plug-in watt meter to measure it. Cost uses an example price of 17 cents per kWh.
| Device | Watts | Cost per hour | Typical use | Cost per month at that use |
|---|---|---|---|---|
| LED light bulb | 9 W | $0.002 | 5 h/day | $0.23 |
| Phone charger | 15 W | $0.003 | 3 h/day | $0.23 |
| Wi-Fi router and modem | 15 W | $0.003 | 24 h/day | $1.84 |
| CPAP machine | 40 W | $0.007 | 8 h/day | $1.63 |
| Mini fridge (average) | 30 W | $0.005 | 24 h/day | $3.67 |
| Full-size refrigerator (average) | 60 W | $0.010 | 24 h/day | $7.34 |
| Laptop | 60 W | $0.010 | 4 h/day | $1.22 |
| Box fan | 50 W | $0.009 | 8 h/day | $2.04 |
| Ceiling fan | 75 W | $0.013 | 8 h/day | $3.06 |
| LED TV | 100 W | $0.017 | 4 h/day | $2.04 |
| Electric blanket | 100 W | $0.017 | 8 h/day | $4.08 |
| Desktop computer | 200 W | $0.034 | 6 h/day | $6.12 |
| Microwave | 1,000 W | $0.170 | 15 min/day | $1.28 |
| Coffee maker | 1,000 W | $0.170 | 30 min/day | $2.55 |
| Window AC (10,000 BTU, average) | 900 W | $0.153 | 8 h/day | $36.72 |
| Space heater | 1,500 W | $0.255 | 8 h/day | $61.20 |
| Hair dryer | 1,500 W | $0.255 | 15 min/day | $1.91 |
| Electric dryer | 5,400 W | $0.918 | 1 h/day | $27.54 |
Cost per hour is watts ÷ 1,000 × the price per kWh. Devices that cycle on and off, like refrigerators and air conditioners, use less than their running watts on average, which is why the figures above are averages.
Solar recharging
Panels are rated in watts at ideal conditions. In practice you get about 75% of that, over the "peak sun hours" a location receives each day, which is about 3 to 6 hours in most of the US and less in winter.
To refill 2,335 Wh a day at 4 sun hours you need about 780 W of panels: four 200 W panels. Check also the unit's maximum solar input in watts, since that caps how fast it can recharge. A 1,000 Wh station with a 200 W solar limit takes at least five hours of full sun to recharge, and often a lot longer.
Power station vs generator
- Power station: silent, clean, safe indoors (no exhaust), instant, and solar-friendly. But its energy is limited, it is expensive per watt-hour, and it struggles with heating and large motors.
- Gas generator: far more energy per dollar, and it can run heavy loads for days with fuel, but it is loud, needs fuel storage, and must be run outdoors, away from windows, because of carbon monoxide. See the generator sizing guide.
Many people use a power station for essentials, electronics and quiet use, and add a generator only if they need to run heavy loads for long periods.
Buying checklist
- Battery chemistry. LiFePO4 (lithium iron phosphate) lasts about 3,000 or more charge cycles; older lithium-ion packs typically 500 to 800.
- Surge rating high enough for your biggest motor, such as a refrigerator compressor.
- Outputs that match your devices: AC outlets, USB-C power delivery, 12 V car socket.
- Recharge options and speed: wall, car and solar, and whether it can charge while powering things (pass-through).
- Weight and size: a 2,000 Wh unit weighs 40 lb or more.
- Warranty and expandability: some allow you to add extra battery packs later.
Tools & materials for this project
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Estimates only. Quantities depend on your materials, site and supplier. Confirm important numbers before you order, and follow local building codes for anything structural.