How much heat-pump and EV load growth wears out a distribution transformer, and how much does smart charging buy back?

research/infra-transformer

Distribution transformer ageing under heat-pump and EV growth: an IEEE C57.91-form thermal model on TMY weather and a standard load profile; loss of life stays under 0.01%/yr until ~50% of homes electrify, then 5.6%/yr at 100% with uncoordinated charging against 1.07%/yr with valley-filled charging (constants swept, not verified).

8 tests

What it found

An hourly IEEE C57.91-form top-oil and hot-spot model (ageing factor exp(15000/383 − 15000/(θ_H+273)), 180,000 h normal life) driven by 10 homes: the BDEW H0 profile at 10,800 kWh/yr each, NREL TMY ambient, a heat pump with a temperature-dependent COP, and EV charging either on arrival or valley-filled overnight. On a transformer sized at 0.5 per unit of baseline peak in Greensboro weather, loss of life is 0.0019 %/yr at baseline, 0.0075 at 50 % of homes with a heat pump and an EV, and 5.6 %/yr at 100 % with uncoordinated charging (about 18 years to end of life) against 1.07 %/yr with smart charging. Smart charging removes an EV-only load entirely (0.035 to 0.0026 %/yr) but not coincident heat-pump cold-snap peaks; at 0.7 per unit every heat-pump case fails. Uniform growth of 1.16–1.28× doubles loss of life but 2.2–3.1× is needed to reach the rated-life rate. Limits: the standard’s constants (55 K top-oil rise, R 3.2, n=m=0.8, τ 3 h) are recalled, not verified, and are swept; heat pumps are fully coincident with no setback; TMY weather rather than extremes; a German load shape on US weather; smart charging has perfect foresight.

A figure from its own output

Figure produced by research/infra-transformer: lol — infra-transformer/experiments/lol.svg, written by the project's own experiment code.

Paper, code and results

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Produced with AI assistance (Claude). Results are from the code in this repository and are simulated or stylised unless the abstract says otherwise; nothing here implies affiliation with or endorsement by any lab, researcher or company cited. MIT licensed.