Portable Power Calculators
Size a power station with your actual devices, hours and charging setup. No signup, no saved inputs and no hidden math — just practical estimates and links to the relevant reviewed picks.
Choose a calculator
All three calculators are available now. Choose your load type to get transparent battery and runtime math.
Watt-Hour Calculator
Add devices, AC/DC efficiency, days, solar and a safety margin to estimate battery Wh and inverter watts.
Size your power station → Available nowCPAP Battery Calculator
Estimate nights of CPAP runtime with humidifier settings, heated tubing and AC or 12V DC power.
Estimate your CPAP runtime → Available nowStarlink Mini Power Calculator
Plan off-grid internet runtime from dish draw, hours online, battery capacity and optional solar.
Estimate your Starlink runtime →Calculator FAQ
Are these power calculators free to use?
Yes. Every calculator is free, runs entirely in your browser and does not require an account.
Does the calculator save my device list?
No. Your inputs are not stored on a server. Copy the result summary or the prefilled share URL if you want to keep a calculation.
Why does the watt-hour calculator include efficiency losses?
A power station loses energy while converting battery power for your devices. The calculator uses 0.85 efficiency for AC loads and 0.95 for compatible 12V DC loads, then adds a separate safety margin.