Distribution Transformers


Distribution transformers include the metal boxes found in subdivisions and cylinders found on utility poles across the nation that serve the important function of reducing electricity voltage to levels needed to power lights, appliances, equipment and other products. Utilities generally own and operate "liquid-immersed" transformers, which use oil as a coolant and are usually installed outdoors, that deliver electricity to their customers. Low-voltage dry-type (LVDT) and medium-voltage dry-type (MVDT) transformers, which use air rather than oil as an insulation medium, are generally installed inside buildings and are owned by the building owner. 


The current standards for distribution transformers took effect in 2016. The standards required only a modest increase in efficiency, particularly for liquid-immersed transformers. 

In 2023, DOE proposed amended standards that would reduce fleet energy losses by about 36%, 47%, and 24% for liquid-immersed, LVDT, and MVDT transformers, respectively. 


Distribution transformers are generally very efficient — electricity losses are usually below 1-3%. However, since almost all electricity passes through one or more transformers, even small improvements can yield very large national energy savings. In general, transformers can be made more efficient by using better quality windings, improved core designs, and lower-loss core electrical steel. Low-loss amorphous metal cores offer the biggest opportunity to improve transformer efficiency. 

Savings through what year?: 2045
Energy saved (quads): 0.92
CO2 savings (million metric tons): 82.2
Net present value savings ($billion) 3% discount rate: 3.12
Net present value savings ($billion) 7% discount rate: 0.58


Federal Date States
Potential Effective Date of Updated Standard 2024
Updated DOE Standard Due 2021
2nd Federal Standard Effective 2016
2nd Federal Standard Adopted (DOE) 2013
1st Federal Standard Effective 2010
1st Federal Standard Adopted (DOE) 2007
Test Procedure - Last Revised - Active Mode 2006
EPACT Initial Federal Legislation Enacted 1992

Timeline reflects state standards from 2001 to present; federal standards from inception to present.