Losses

Losses

 

An ideal transformer would have no losses and therefore would be 100% efficient. In practice however, energy is lost due to the resistance of the windings, (copper loss), and to magnetic effects in the core, (iron loss). Transformers in general are very efficient, large power transformers may have an efficiency as high as 99%. Small transformers, such as those used to power consumer electronics, may be less than 85% efficient.