Dr. Tierney is an expert on energy policy and economics, specializing in the electric and gas industries. She has consulted to companies, governments, nonprofits, and other organizations on energy markets, as well as economic and environmental regulation and strategy. Her expert witness and business consulting services have involved industry restructuring, market analyses, utility ratemaking and regulatory policy, clean energy regulatory policy, transmission issues, wholesale and retail market design, and resource planning and procurement. Dr. Tierney is a former assistant secretary for policy at the US Department of Energy, state cabinet officer for environmental affairs, and state public utility commissioner. She chairs the board of directors of Resources for the Future; serves on the external advisory board of the National Renewable Energy Laboratory; and is a member of the boards of directors of the World Resources Institute, the Alfred P. Sloan Foundation, the Barr Foundation, and other organizations. She has published widely, frequently speaks at industry conferences, and has lectured at many leading universities.