Uniformat D5010

Pad-mounted transformer

A pad-mounted transformer lasts about 32 years, the median of 3 published sources, which state 30–32 years.

Also listed as Transformer, pad-mounted liquid-filled, pad mount transformer

• Confidence C
• Version 0.5.0 (permanent link)
• Reviewed 2026-10-23

Service life

Years in service. The band runs from the shortest to the longest life the sources state, so it shows how much they disagree, not how long 80% of units last. The line is the median of the stated lives.

Work out when yours is due for replacement

Basis

• 30 years · CNA e-Tool Estimated Useful Life Table, p3 · HUD CNA 3.2.8.2.3 “Transformer” — U.S. Department of Housing and Urban Development (planning life)
  Same life for family and elderly properties. US multifamily housing. HUD's row is a site electric utility transformer.
• 32 years · Energy Conservation Program: Energy Conservation Standards for Distribution Transformers (final rule), 78 FR 23336, April 18, 2013, p42 · IV.F.2.g “"DOE estimated, based on a report by Oak Ridge National Laboratory, that the average life of distribution transformers is 32 years." Table (PDF p.38, printed 23373): "mean lifetime for both liquid and dry-type transformers assumed to be 32 years."” — U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy (planning life)
  Printed page 23377. Low-voltage and medium-voltage dry-type transformers (owned by building owners) and liquid-immersed transformers (mostly utility-owned, including pad-mounted). One mean for both.
• 32 years · Energy Conservation Program: Energy Conservation Standards for Distribution Transformers (final rule), 89 FR 29834, April 22, 2024, p113 · IV.F.8 “Transformer Service Lifetime: "a distribution of lifetimes, with an estimated average of 32 years and a maximum of 60 years"” — U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy (planning life)
  Printed page 29946. Covers all distribution transformers, including low-voltage dry-type (building dry-type) and medium-voltage liquid-immersed (pad-mounted). Mean of a distribution; the maximum is 60 years. Same value also stated on p.5 (printed 29838) and in Table IV summary on p.101 (printed 29934).

How sources are chosen and recorded: sourcing policy.

Preventive maintenance

9 tasks in 2 work orders. Intervals that fall due together are one visit: the every 2 years visit also covers the annual tasks.

1. 1
2. 2
3. 3
4. 4
5. 5
6. 6
7. 7
8. 8
9. 9
10. 10
11. 11
12. 12Annual

Months from the schedule start. Download the tasks as CSV for a CMMS, or ask the MCP tool get_pm_schedule for dated visits.

Frequencies are ISO 8601 durations in the data (P3M = every 3 months).

Open questions

• Every source here is a published planning, design or accounting life. None is observed replacement data.
• Some maintenance intervals come from TM 5-692-1, an Army manual for mission-critical (C4ISR) facilities; they may be tighter than typical commercial practice.

Know the answer? Send it with a source to [email protected].

Cite this

Citation

unfinished.one (2026). Transformer, pad-mounted liquid-filled, v0.5.0. https://unfinished.one/c/transformer-pad-mounted/v/0.5.0

BibTeX

@misc{unfinished_transformer_pad_mounted_0_5_0,
  title = {Transformer, pad-mounted liquid-filled},
  author = {{unfinished.one}},
  year = {2026},
  version = {0.5.0},
  url = {https://unfinished.one/c/transformer-pad-mounted/v/0.5.0},
  note = {CC BY 4.0}
}

Licence CC BY 4.0 · How to cite · JSON · Versions: 0.5.0, 0.4.0, 0.3.0, 0.2.0, 0.1.0