Lexicon DIY-Knowledge

Total efficiency


Rendimiento final

Degré d'efficacité global

If several machine components are linked together, their total efficiency is the product of the individual efficiency ratios of the machine components.


A percussion hammer consists of an electric motor, a transmission and an impact system. The individual efficiency ratios could be 85% for the motor, 95% for the transmission and 80% for the cooling fan. The calculation goes like this:

0.85 x 0.95 x 0.8 = 0.646 or 64.6%

With a total efficiency of 64.6% and an electric power input of 1.000 watt, you have an effective mechanical output power of 646 watt, available at the chisel.

This calculation example shows the importance of quality and the efficiency ratio of the individual components. For this reason established manufacturers of quality power tools state for the users information the power output in addition to the power input in their catalogues. No name products often boast with the high power inputs of their appliances, but due to low quality standards and the bad efficiency ratio they rarely specify the actual power output. Often only power is written on the rating plate and the consumer is consciously mislead!