"Efficiency"

In electrochemical processes like electroplating, how much reaction happens (i.e., how much metal deposits on the parts, how much metal dissolves from the anodes) is basically directly proportional to the current x the time. This is explained by Faraday's Law.

However, some amount of the electricity is usually 'wasted' towards electrolyzing water into hydrogen and oxygen gas instead of depositing or dissolving metal. The proportion of the electricity which is not wasted but deposits or dissolves metal is called the efficiency.

Some plating solutions under proper circumstances achieve nearly 100% efficiency; some, like chrome plating, rarely achieve even 25%.