Use of lower-loss medium-voltage, liquid-immersed distribution transformers can yield large energy and monetary savings over their lifetime, improving the bottom line of utilities and their ratepayers. Depending on load factor and output power, distribution transformer losses can be reduced by 11 to 29 percent.

Avoiding Distribution Transformer Energy Waste

The use of lower-loss medium-voltage, liquid-immersed distribution transformers that go beyond the U.S. Department of Energy’s conservation standards can yield large energy and monetary savings over the units’ lifetime.

What constitutes a meaningful level of savings while still being cost effective?

Find out in the ENERGY STAR Guide to Buying Energy Efficient Distribution Transformers (PDF, 1021 KB)

This guide specifies energy efficiency criteria for distribution transformers by load factor, addresses the cost effectiveness of energy efficient transformers, and discusses regulatory and purchasing considerations, as well as procurement planning.

The guide applies to medium-voltage, liquid immersed distribution transformers, specifically:

Type Liquid-Immersed,
Excluding vault-type
Capacity 10 kVA – 500 kVA single-phase;
2500 kVA three-phase
Voltage Input: 34.5 kV or less;
Output: 600 V or less
BIL1 ≤ 150 kV

Who should use this guide?

The primary audience for the buying guide is utility purchasers, but the guide should also be useful to other purchasers of applicable transformer types, including military bases, corporate and college campuses, and solar and wind developers. In addition, utility regulators and energy efficiency advocates may find the document useful for defining what it means to purchase an energy-efficient distribution transformer.

1 Basic Impulse Insulation Level (BIL) is the measure of resistance to very large changes in voltage, like those from a lightning strike.