The prefix "iso" means "same"/"equal". E.g. isobars (same pressure) on a weather map, isotopes (same place) on the periodic table, isomorphic (same structure),

The prefix "iso" means "same"/"equal". E.g. isobars (same pressure) on a weather map, isotopes (same place) on the periodic table, isomorphic (same structure), etc. Here iso-power means comparing performance for the same power usage, and iso-performance means comparing power usage for the same performance.