Recovery efficiency
Recovery efficiency is the share of the fuel or electricity input that actually ends up in the water while the unit is heating. Gas units run about 80–99%; heat pump models exceed 100% several times over because they move heat rather than make it.
Recovery efficiency captures steady-state heating performance, while UEF adds standby and cycling losses over a full day — a unit can have excellent recovery efficiency but mediocre UEF if its tank loses heat quickly.
For gas storage units, condensing models reach the high 90s by extracting heat from exhaust gases that non-condensing designs vent outdoors.