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Specifications line up neatly in a table and still mislead, because the number that decides whether a product works for you is rarely the headline one. Four things are worth checking column by column before you weigh price.

Surge against running watts. A fridge, pump or compressor draws several times its running figure for the instant it starts. Two units with identical continuous ratings can differ entirely in whether they start your appliance, and the surge column is where that shows.

Usable against rated capacity. Watt-hours on the box are gross. Inverter conversion costs roughly 10–15%, and some chemistries should not be run flat. Compare what you can actually take out, not what is printed on the label.

Cycle life against warranty. LiFePO4 cells are typically rated for 3,000–5,000 cycles against 500–800 for older NMC packs. On a product you expect to keep for a decade, that gap matters far more than a few hundred watt-hours of capacity.

What the price excludes. Solar panels, transfer switches, extra battery modules and installation are frequently sold separately. The cheapest column here is not always the cheapest working system.

If you are not sure which figures apply to your situation, the wattage calculator turns an appliance list into the two numbers — continuous watts and watt-hours per day — that these columns are answering.