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Distribution Transformers

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As defined in the Code of Federal Regulations (CFR), “distribution transformer” means a transformer that (1) has an input voltage of 34.5 kV or less; (2) has an output voltage of 600 V or less; (3) is rated for operation at a frequency of 60 Hz; and (4) has a capacity of 10 kVA to 2500 kVA for liquid-immersed units and 15 kVA to 2500 kVA for dry-type units. The term “distribution transformer” does not include a transformer that is an: autotransformer; drive (isolation) transformer; grounding transformer; machine-tool (control) transformer; nonventilated transformer; rectifier transformer; regulating transformer; sealed transformer; special-impedance transformer; testing transformer; transformer with tap range of 20 percent or more; uninterruptible power supply transformer; or welding transformer.10 CFR 431.192

Manufacturers have been required to comply with the U.S. Department of Energy (DOE) energy conservation standards for distribution transformers since 2007.

Current Standard | Current Test Procedure | Ongoing Rulemaking for Standards | Ongoing Rulemaking for Test Procedure | Helpful Links

Recent and Ongoing Activities

The U.S. Department of Energy (DOE) has published a Federal Register Final Rule (FR) pertaining to energy conservation standards for Distribution Transformers. The Energy Policy and Conservation Act (EPCA), prescribes standards for various consumer products and certain commercial and industrial equipment, including Distribution Transformers. In this final rule, DOE is adopting amended standards for distribution transformers. DOE has determined that the amended standards for these products would result in significant conservation of energy and are technologically feasible and economically justified.

  • The effective date of this rule is July 8, 2024. 
  • Compliance with the amended standards established for distribution transformers in this final rule is required on and after April 23, 2029.


Final Rule

Notice of proposed rulemaking and announcement of public meeting

Notice of proposed rulemaking; Comment Extension

Webinar and Availability of the Preliminary TSD; Reopening of public comment period

Notification of a webinar and availability of preliminary TSD

Request for information

  • Federal Register, 84FR28239 (June 18, 2019)

The distribution transformers energy conservation standard rulemaking docket EERE–2019–BT–STD–0018 contains all notices, public comments, public meeting transcripts, and supporting documents pertaining to this rulemaking.

Public Meeting Information:

There is no public meeting scheduled at this time. 

Submitting Public Comments

Comment period is closed.

Test Procedure

Final Rule
  • Federal Register, 896FR51230 (September 14, 2021).
Notice of Proposed Rulemaking
  • Federal Register,  84FR20704 (May 10, 2019)

Request for Information; Reopening of the Comment Period

Request for Information

The docket EERE-2017-BT-TP-0055 contains all notices, public comments, and supporting documents pertaining to this rulemaking.

Public Meeting Information

There is no public meeting scheduled at this time.

Submitting Public Comments

The comment period is closed.

For the latest information on the planned timing of future DOE regulatory milestones, see the current Office of Management and Budget Unified Agenda of Regulatory and Deregulatory Actions. All planned dates are preliminary and subject to change.

Current Standard

Distribution transformers manufactured and distributed in commerce, as defined by 42 U.S.C. 6291(16), must meet the energy conservation standards specified in the Code of Federal Regulations at 10 CFR 431.196.

Current Test Procedure

To determine that distribution transformers that are currently manufactured or distributed into commerce are in compliance with DOE standards, manufacturers must follow the test procedure methods specified at 10 CFR 431.193 and Appendix A.

Helpful Links


DOE has established regulations on certification, compliance, and enforcement in the CFR at 10 CFR Part 429.  These regulations cover statistical sampling plans, certified ratings, certification reports, record retention, and enforcement.  More information on these regulations is available here.


For information on current test procedure waivers, see DOE’s Waivers webpage

For information about obtaining test procedure waivers, see 10 CFR 430.27.


DOE's Office of Hearings and Appeals has not authorized exception relief for distribution transformers.

For information about obtaining exception relief, see 10 CFR part 1003.

Guidance and Frequently Asked Questions

For information on further guidance and answers to Frequently Asked Questions on all covered products, see DOE’s Further Guidance database

State Exemptions to Federal Pre-emption

DOE has not exempted any state from this energy conservation standard. States may petition DOE to exempt a state regulation from preemption by the Federal energy conservation standard. States may also petition DOE to withdraw such exemptions. For details, see 10 CFR part 431, subpart V or subpart W.

Contact information

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