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Short reads on the numbers behind the tools.

Updated

The numbers on the box

What watts, watt hours and starting watts mean, and how to read them off a label.

  • Watts vs watt hours, explained

    Watts say whether a power station can run an appliance. Watt hours say for how long. The difference, with worked examples and the formulas.

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  • Why you get less than the rated capacity

    A power station rated 1,000 Wh delivers about 850 Wh at its outlets. Where the rest goes, why we count 85%, and when to change it.

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  • Starting watts explained

    Why motors and compressors need more watts to start than to run, how a power station surge rating covers the start, and how the calculator checks it.

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  • How to read an appliance label for watts

    Find the watts on an appliance rating label, turn volts and amps into watts, read an EnergyGuide label for daily energy, then enter it in the calculator.

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Battery, solar and backup

Battery chemistry, refilling from the sun, and what a backup mode does when the grid drops.

  • LiFePO4 vs NMC batteries in power stations

    LiFePO4 and NMC batteries compared on weight, cycle life, heat stability and cobalt, with the cycle ratings published for the stations in our data set.

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  • How much solar to recharge a power station

    The solar recharge math: panel watts times peak sun hours times 0.75, capped at the station limit, with refill times and panel sizes worked out.

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  • Power station backup mode (UPS) explained

    How backup mode on a power station works, what the switch time in milliseconds means for a computer, a fridge or a CPAP, and what each maker states.

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Deciding what to buy

The common questions before a purchase, answered with the same math as the calculator.

  • Can a power station run a refrigerator?

    Starting watts, daily energy and the runtime math for a refrigerator on a portable power station, worked out for 54 stations.

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  • Power station or generator?

    What a portable power station can and cannot replace: electric heat, air conditioning and 240 V loads, with the energy math and the safety rules.

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Tools and reference