Dongan’s 41, 42, 43 and 44 series are designed to meet the D.O.E. Energy Efficiency guidelines established under EPACT in 2005. This was sued to establish energy conservation standards for various consumers, commercial and industrial products including certain types of General Purpose Transformers.
This applies to transformers 15kVA and larger and establishes a minimum 97% efficiency level.
Please see the following Datasheets for more information and which models this effects: