Power bank prices per 100 Wh

A pack price and a mAh figure don’t tell you what the energy costs. Labels print capacities at different voltages, many add a second, smaller figure at 5 V, and a two-pack is easy to count once. 20,000 mAh at the cells’ 3.7 V is 74 Wh.

Amazon sorts power banks by price and filters them by mAh, with no price per watt-hour. Galaxus prices and sorts its own range per Wh, in 7 European countries. Stiftung Warentest measures the usable energy of the 24 banks it tested and lists their declared Wh, but puts no price on a watt-hour.

We do it for Amazon’s listings, in 10 Amazon stores from the US and the UK to Japan and India. We turn the capacity each listing states into watt-hours (mAh × 3.7 V, or the stated Wh where it agrees), count every bank in a pack and rank a category by the price of 100 Wh. A capacity the listing’s weight or price cannot back gets no price per Wh; a value resting on a resolved conflict is marked ~.