Power Station Sizing Calculator
Add the devices you want to power, enter how long you'll run each one, and we'll calculate the watts and watt-hours you need — with a 20% safety buffer built in. Use it to answer: what size power station do I need?
Devices & Appliances
Results
Tips
- • Wattage labels on devices are maximum draw — actual use is usually less.
- • Motor-driven appliances (fridges, AC) have a startup surge 2–3× their running watts.
- • LiFePO4 batteries support more cycles and deeper discharge than standard Li-ion.
- • For solar recharging, divide your required Wh by peak sun hours in your region.
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Power Station Sizing FAQ
Quick answers on sizing a portable power station with the power sizer above.
What size power station do I need?▾
Add up the watts of the devices you want to run, multiply by the hours you will use them, then add a safety buffer. The calculator above does this for you and also checks your peak load against typical inverter sizes.
How do I use a power sizer?▾
Enter each device, its running watts, hours per day, and quantity. The power sizer totals your daily watt-hours, adds efficiency losses and a safety buffer, then recommends a capacity class and minimum watt-hours.
What is the difference between watts and watt-hours?▾
Watts measure instantaneous power (how much a device draws right now), while watt-hours measure energy over time. A 100W device run for 5 hours uses 500Wh of energy.
How long will a power station run my refrigerator?▾
Divide the station's usable watt-hours by the fridge's typical running watts, then allow for startup surge and the fact that fridges cycle on and off. Use the calculator with a measured or estimated daily consumption for your appliance.
How much capacity do I need for camping?▾
A weekend trip for phones, lights, and a laptop often fits 300–600Wh, while a cooler, CPAP, or longer stays usually need 600Wh or more. Enter your exact devices above for a specific number.
The sizing math, in one line
Capacity (Wh) = Total device watts × Hours of runtime
Required capacity = Daily Wh ÷ Efficiency + 20% safety bufferSources: U.S. Energy Information Administration (EIA), U.S. Department of Energy (DOE), and National Renewable Energy Laboratory (NREL) appliance and outage guidance.
Found your capacity? Compare power stations.
WhichWatts tracks 500+ power stations with real-time prices, sorted by cost per watt-hour.