Tim Brennan focuses on public policies involving monopolies and market power, and on assessing methods for policy evaluation. He looks particularly at issues associated with restructuring the electricity sector and opening electricity utilities and markets to competition. Specific topics in recent publications include real-time pricing, climate change, network effects, decoupling electricity revenues from use, energy conservation policy, and space launch risk.

His current research examines rationales for energy efficiency policies, the limits of cost-benefit analysis in climate policy, and the role of behavioral economics in energy and environmental policy. He has been co-author of two books on the deregulation of electricity markets and has analyzed constitutional requirements for compensation for public use of private land. He has studied privacy and environmental law enforcement related to remote-sensing satellites and is working on the roles of prizes in technological innovation and on assessing liability rules for space launches. Brennan also addresses issues in antitrust law, telecommunications policy, copyright, and the philosophy of economics. He has presented his research to numerous government, professional, and academic institutions in the U.S. and internationally, including Austria, Australia, England, France, Germany, Ireland, Mexico, New Zealand, Sweden, and Uzbekistan.