Management Team

Gary Epstein

Gary Epstein is the President and Founder of ERS and is a US Green Building Council LEED Accredited Professional. His interdisciplinary skills are in the energy engineering and environmental consulting fields. His current work and areas of expertise include energy technology characterization, impact evaluation, research, and assessment; energy code development and consulting; assessment of environmental impacts of energy use and conservation; and development, planning, and evaluation of utility and government resource conservation programs.

Gary is the past chair of the AESP Energy Services and Technology Committee and his work has been published in numerous professional journals and conference proceedings. Mr. Epstein holds a M.S. from the University of Massachusetts and a B.S. from the State University of New York at Buffalo, both in Mechanical Engineering. You can contact Gary at This e-mail address is being protected from spambots. You need JavaScript enabled to view it. or 978-521-2550, x225.

Mark D'Antonio

Mark D’Antonio is a Senior Vice President at ERS. He is an experienced technical manager of a wide array of energy efficiency services including industrial efficiency and productivity assessments, feasibility studies for renewable and distributed generation projects, compressed air system evaluations, site survey and implementation inspection services, outreach, utility program planning, and energy-related trainings.

Mark’s work has been published in numerous professional journals and conference proceedings. He holds a BS in Mechanical Engineering from the University of Massachusetts and is a LEED Accredited Professional. You can contact Mark at This e-mail address is being protected from spambots. You need JavaScript enabled to view it. or 978-521-2550, x251.

Brian McCowan

Brian McCowan, LC, is Vice President of Technology and Development at ERS, with interdisciplinary skills in the energy engineering, lighting, environmental, and renewable technology consulting fields. As a licensed construction supervisor and certified lighting designer, his expertise in project design and management is utilized throughout ERS’s scope of services. Additionally, Brian has over 20 years of experience in the training of energy system professionals.

In recent years, Brian has spent considerable time providing consulting services in support of enhanced compliance with new energy codes. He is currently involved in ERS’s development effort for web-based resources to support energy code understanding and compliance. Mr. McCowan is an active participant in the Association of Energy Service Professionals (AESP) Energy Technology Committee. He holds a bachelor’s degree from the University of Southern Maine. You can contact Brian at This e-mail address is being protected from spambots. You need JavaScript enabled to view it. or 978-521-2550, x301.

Bruce Harrington

Bruce Harrington is Vice President of Implementation and Operations at ERS. His experience includes over 15 years in the electric utility industry with management and oversight responsibilities for energy efficiency programs, and he has over 20 years experience in management positions for sales, marketing, customer service, and multi-channel marketing.

Bruce has been involved with issues relating to energy efficiency for many years, serving on the DOE advisory council for energy efficient construction standards and representing the Energy Efficient Building Association as their President. He also has extensive knowledge in strategic planning, team building, and new business start-up. He holds an A.S. in Agricultural Mechanization Technology and a B.S. in Business Management from the University of Maine. You can contact Bruce at This e-mail address is being protected from spambots. You need JavaScript enabled to view it. or 207-622-6888, x2703.

Jon Maxwell

Jon Maxwell, PE, is Vice President of Engineering and Evaluation at ERS, with more than 15 years of experience in energy efficiency program evaluation and implementation. He has managed major field data collection efforts for evaluation and load research and has trained more than 200 energy professionals on a wide variety of topics, mostly related to field data collection and analysis. He has conducted more than 100 C/I site visits and led start-up, hiring, training, and project management for four energy audit programs that provided a combined 1,600 audits per year to utility customers.

Jon has published extensively, and he is a Professional Engineer registered in Maryland and Texas, a LEED Accredited Professional, and an EPA Green Lights Surveyor Ally. He holds a M.S. in Mechanical Engineering from Oregon State University and a B.S.E. in Mechanical Engineering and History from Duke University. You can contact Jon at This e-mail address is being protected from spambots. You need JavaScript enabled to view it. or 979-575-1281.

Mary McElhiney

Mary McElhiney is the Director of Business Operations at ERS. Her main responsibilities include outreach and marketing; project development; energy efficiency program management; proposal and report writing, design, and coordination; development and operation of business systems for optimized project management and efficient operations; and application of computerized database and analysis systems for program management. Mary holds a B.A. from Merrimack College and has extensive experience in project management as well as administrative management. You can contact Mary at This e-mail address is being protected from spambots. You need JavaScript enabled to view it. or 978-521-2550, x273.

Sue Haselhorst

Sue Haselhorst is a Director at ERS with over 25 years of experience in the energy efficiency field. She has been project manager for various analytical and technical assessments and multiple evaluations. She has also provided design and construction services for campus energy management systems.

Sue served for eight years as an electric utility program planner and evaluator. She was responsible for the design and implementation of a portfolio of commercial and industrial programs, including the development of strategic account plans for very large customers. She also managed a highly successful community-based pilot program called the Marshfield Energy Challenge. Her areas of expertise include project management, analytics, program impact evaluation, and program design. Sue holds a BS in mechanical engineering from the University of Massachusetts. You can contact Sue at This e-mail address is being protected from spambots. You need JavaScript enabled to view it. or 978-251-2550, x218.

David Reynolds

David Reynolds, PE, LEED AP, CEM, is the California Regional Director at ERS with more than 15 years of experience in the development, management, and implementation of energy efficiency and renewable energy projects and programs. He has developed energy efficiency programs, marketed customer service programs for energy utilities, created strategic energy plans, performed financial and technical analysis for complex energy retrofit projects, and provided regulatory representation in the development of state and local energy policy. He has also conducted hundreds of commercial and industrial energy surveys and assessments in support of energy performance contracting projects and provided technical expertise for more than fifty utility program administrators. David is a Professional Engineer registered in California, a LEED Accredited Professional, a Certified Energy Manager, and a Certified Residential Plans Examiner. He holds a B.S. in Mechanical Engineering from California Polytechnic State University at San Luis Obispo, CA. You can contact David at This e-mail address is being protected from spambots. You need JavaScript enabled to view it. or 916-303-1993.