Energy Manager

ACEEE says new U.S. transformer standards are “a mixed bag”

April 10, 2013 - The U.S. Department of Energy (DoE) issued new energy efficiency standards for electric distribution transformers. In the final rule, relative to a draft standard issued a year ago, ACEEE explains DoE improved the standard for dry-type transformers (those primarily used in buildings) but left the proposed standard for liquid-immersed transformers (those most commonly owned by utilities) unchanged.

April 10, 2013
By Anthony Capkun

“The new standard for dry-type transformers is a good step forward and represents a compromise between the positions of the transformer industry and energy efficiency advocates,” said Steven Nadel, executive director of ACEEE (American Council for an Energy-Efficient Economy). “However, the final standard for liquid-immersed transformers is very disappointing, as it results in little energy savings and represents a continued reliance on 20th Century technology and not 21st Century technology increasingly being used in other countries.”

Distribution transformers lower electricity voltage from the high levels used by utilities to ship power through their systems to the voltage levels used to power electricity-using devices in households and businesses. Transformers dissipate a small amount of power as heat, called transformer electricity losses.

ACEEE says the new standard for dry-type transformers will reduce these electricity losses by 30%, while the new standard for liquid-immersed transformers will reduce losses by just 4% for the most commonly sold products. Energy efficiency advocates, represented by ACEEE, the Appliance Standards Awareness Project (ASAP) and Natural Resources Defense Council (NRDC), had argued for standards that would have cut losses for the largest dry-type transformers by about 40% and most liquid-immersed transformers by 15%.

“By making only a very modest change to the standard, DoE clearly decided to favour the conventional steel transformers,” said Andrew deLaski, executive director of ASAP, adding, “The more energy-efficient amorphous products, which are widely used in China and India, will likely continue to face difficulties in the U.S. market.”


The new standard for dry-type transformers is based on a voluntary industry level called NEMA Premium, developed by the manufacturers’ trade association, the National Electrical Manufacturers Association (NEMA). With this new standard, NEMA Premium transformers will become widely used, although even higher levels of efficiency are achievable and will remain available to consumers. The new standards will take effect in 2016.