About · Last updated June 2026
The Power Station Calculator is a free tool that answers two of the most common questions people ask before buying a portable power station: "what size do I need?" and "how long will it last?" It requires no signup, runs entirely in your browser, and stores none of your data.
Most "power station calculators" online do one of two things badly: they either spit out a single watt-hour number without checking whether the unit's inverter can actually start your appliances, or they ignore the real-world losses (inverter inefficiency and battery depth-of-discharge) that make a "1000Wh" battery deliver far less usable energy. The result is people buying units that are too small to start a fridge, or too weak to run what they planned. We built a tool that handles both the energy (watt-hours) and the power (output and startup surge) sides of the problem.
Sizing adds up each appliance's running watts × hours, then pads the total by about 15% for inverter inefficiency and 25% so you're not draining the battery to empty. Output requirements account for the startup surge of motor- and compressor-driven appliances, which can briefly draw several times their running wattage. Runtime estimates divide usable capacity by the device's draw and apply a typical inverter efficiency factor. Appliance wattages are drawn from manufacturer specifications and standard reference figures, including data published by the U.S. Department of Energy. All figures are estimates — your real results depend on your specific equipment, battery age, and temperature.
This tool is built and maintained by the Rytell tools team, which produces a network of free, no-signup calculators and guides. Our approach is to favor accurate, honest outputs — including the costs and limitations most tools leave out — over flattering oversimplifications. We are not affiliated with any power station manufacturer, and product tiers shown are general guidance, not endorsements.
This site is free and supported by display advertising (Google AdSense) and affiliate commissions — including the Amazon Associates program — earned when you buy through links here, at no extra cost to you. Affiliate relationships never change the calculator's outputs, which are based purely on your inputs and standard formulas. See our Privacy Policy for how advertising and cookies work on this site.