Public utility commissions (PUCs) are small state-level regulatory institutions in the United States adjudicating conflicts over electrical power rates, energy generation, electric vehicle infrastructure, and energy efficiency among other issues. PUCs are critically understudied institutions given their central role in addressing climate change. This is partially due to a lack of data related to public utility commissioners. What are the characteristics of these energy system regulators? I make an initial contribution with expansive original data on the professional backgrounds of the over 800 commissioners who served from 2000 to 2020. Particular attention is given to ties to the utilities PUCs regulate, the fossil fuel industry, and environmental positions in government, business, and advocacy. Utility industry backgrounds have become more frequent, but there has been a greater increase in environmental connections in recent years. These data and findings can stimulate additional research on the increasing environmental responsibilities of PUCs.