Most AC power distribution transformers are 95% or better. As of 2016 the US EPA mandated even greater efficiency of 97% or greater: https://www.ecfr.gov/curre

Most AC power distribution transformers are 95% or better. As of 2016 the US EPA mandated even greater efficiency of 97% or greater: https://www.ecfr.gov/current/title-10/chapter-II/subchapter-D/part-431#subject-group-ECFRf791a7b3e315557 https://www.ecfr.gov/current/title-10/chapter-II/subchapter-...