Management Team

George Sakellaris is Chief Executive Officer and Chairman of the Board of Directors of Ameresco, Inc. (NYSE:AMRC), a leading energy infrastructure company delivering integrated solutions to create reliable power and modernize infrastructure.

A visionary and entrepreneur, he founded Ameresco in April 2000. He aspired to build an entirely product-neutral and supplier-independent energy company that had the skills, capabilities and foresight to create solutions that went beyond just conservation; one that addressed a customer’s entire energy stream including supply and demand, energy efficiency and renewable energy.

Early in his career, Mr. Sakellaris worked at the utility New England Electric System (NEES), where he welcomed the challenge to establish NEES Energy, a company that would promote energy efficiency, thereby avoiding the need to build new power generation plants. He then purchased the business known as NEES Energy in 1991 and renamed it NORESCO. He built NORESCO into an industry-leading independent energy services company before selling it to Equitable Resources in 1997, where he continued to lead NORESCO and was also appointed as a Senior Vice President of Equitable Resources (NYSE:EQT), a Fortune 500 Energy Company.

Today, Mr. Sakellaris leads Ameresco, a public company dedicated to helping customers create reliable power, modernize infrastructure, enhance resilience, and achieve their long-term energy goals. The company is a trusted full lifecycle partner that helps organizations create reliable power, modernize infrastructure, improve resilience, and optimize energy performance through a comprehensive portfolio of advanced power solutions, infrastructure modernization, distributed energy resources, and smart building technologies. Headquartered in Framingham, MA, Ameresco has more than 1,500 employees providing local expertise in North America and Europe.

With more than 30 years of experience in the energy industry, Mr. Sakellaris has pioneered innovative business models that help organizations implement energy infrastructure, efficiency, resilience, and renewable energy solutions while aligning long-term operational and financial objectives. His dedication and influence in promoting energy efficiency dates back to his involvement with the Electrical Power Research Institute (EPRI) where he championed the development of demand side management (DSM) programs that were widely implemented across the country. Additionally, he was a founding member of the National Association of Energy Service Companies (NAESCO) where he served as the first president and advocated for the new industry.

Mr. Sakellaris earned both M.B.A and M.S.E.E. degrees from Northeastern University and a B.S.E.E. degree from the University of Maine - Orono. In May 2012, the University of Maine granted him an Honorary Doctorate for his lifetime of achievements, recognizing his dedication and exemplary leadership in the field of energy efficiency and renewable energy. In May 2017, the University of Maine honored Mr. Sakellaris with his induction as a Hall of Fame Member of the Francis Crowe Society.

He has received numerous honors recognizing his leadership in the energy industry, including the Northeast Clean Energy Council’s Decade of Influence Award in 2017 and CIO Review’s recognition of Ameresco among the 20 Most Promising Energy Technology Solutions Providers in 2016. Earlier accolades include the Finance Monthly CEO Award (2015), Ernst & Young Entrepreneur of the Year (New England – Energy, Cleantech & Natural Resources, 2011). In 2020, he was named an Environment + Energy Leader 100 Honoree, received a Silver Best in Biz Award for Executive of the Year, and was a finalist for the S&P Global Platts Global Energy Awards – Lifetime Achievement.

Nicole Bulgarino serves as Co-President of Ameresco, a leading energy infrastructure company delivering integrated solutions that create reliable power and modernize infrastructure. She plays a pivotal role in advancing the company's strategic vision, driving growth, operational alignment, and execution across the organization. In addition to her enterprise-wide leadership responsibilities, Ms. Bulgarino leads Ameresco’s work supporting data centers and large energy infrastructure projects with advanced power solutions, while continuing to guide the company’s Federal Solutions business.

Ms. Bulgarino oversees the development and delivery of advanced power and integrated energy infrastructure solutions for data centers, utilities, federal agencies, and other large energy users. These solutions help customers secure reliable power, strengthen resilience, and support mission-critical operations and long-term growth.

A licensed professional engineer, Ms. Bulgarino has spent more than 25 years developing and executing integrated energy infrastructure and power solutions through diverse contract structures. She has overseen the development, implementation, and operation of more than $6 billion in energy projects, ranging from utility-scale renewable energy and battery storage projects to major energy infrastructure upgrades at federal facilities nationwide, including the first comprehensive onsite generation, energy storage, and microgrid projects deployed on U.S. military installations.

Leading a team of more than 380 professionals specializing in engineering, commissioning, construction, operations and maintenance, and long-term performance assurance, Ms. Bulgarino has helped position Ameresco as a leader in delivering guaranteed energy savings through infrastructure modernization projects. Under her leadership, the company has secured repeat business with the Department of Defense, the Department of Energy, the General Services Administration, the Department of Veterans Affairs, and the Department of Justice, among other civilian agencies. Her team also supports investor-owned utilities, municipal utilities, and electric cooperatives with innovative and resilient power solutions.

Throughout her career, Ms. Bulgarino has demonstrated a strong record of leadership, strategic execution, and customer-focused innovation. She has led the development of complex energy infrastructure and power solutions, negotiated and executed a broad range of third-party financed contractual arrangements, managed large-scale project implementation, and served as a featured speaker on technical and business topics at major industry conferences and events. She combines deep technical expertise and operational leadership with a strategic vision for long-term growth and organizational success.

Her contributions have been recognized through numerous industry awards and accolades, including the Stevie® Climate Hero of the Year Award (2025), Energy Storage Report's Top 40 Women Leaders in Energy Storage (2022), and finalist recognition for the S&P Global Platts Rising Star Individual Award (2021).

Ms. Bulgarino earned a Bachelor of Science degree in Chemical Engineering from the University of Tennessee and an Executive Management and Leadership Certificate from the Massachusetts Institute of Technology.

Peter Christakis serves as Chief Operating Officer of Ameresco, a leading energy infrastructure company delivering integrated solutions that create reliable power and modernize infrastructure. In this role, he drives consistency across project execution and risk management, reinforcing the company's focus on disciplined delivery as Ameresco continues to scale. Mr. Christakis also oversees Procurement, Health & Safety, U.S. solar and battery operations, and the company's European operations, ensuring cohesive operational leadership across these critical functions.

In his long-standing leadership at Ameresco, Mr. Christakis has managed over $5 billion in revenue generating projects that comprised complex energy performance contracts, solar and battery installations, large scale infrastructure, and multi-discipline turnkey installations.

With over 33 years of experience in the energy industry, Mr. Christakis has been instrumental in expanding Ameresco’s portfolio of projects in the US and Europe. His deep understanding of the market and commitment to operational excellence, infrastructure modernization, and customer success have enabled Ameresco to stay at the forefront of the energy infrastructure industry. Under his leadership, the company has increased its project portfolio and enhanced its reputation as a trusted partner in delivering integrated energy infrastructure solutions.

Mr. Christakis earned a B.S. in electrical engineering from Northeastern University. He is a Certified Energy Manager and holds the following licenses in multiple states: Master Electrician, Journeyman Electrician, Unlimited General Contractor, and Construction Supervisor.

Lou Maltezos serves as Co-President of Ameresco, a leading energy infrastructure company delivering integrated solutions that create reliable power and modernize infrastructure. He plays a pivotal role in advancing the company's strategic vision, driving growth, operational alignment, and execution across the organization. In addition to his enterprise-wide leadership responsibilities, Mr. Maltezos oversees Ameresco's unified non-Federal project organization to strengthen alignment and scale across the company's operations, while continuing leadership of Smart Building Solutions and Ameresco Canada.

Mr. Maltezos oversees the development and delivery of integrated infrastructure modernization solutions that help organizations improve operational performance, reduce energy costs, strengthen resilience, and support long-term growth. These solutions include building controls, energy efficiency upgrades, advanced metering infrastructure (AMI), and behind-the-meter distributed energy resources.

Since joining Ameresco in 2004 through the acquisition of Exelon's energy savings performance contracting business, Mr. Maltezos has played a key role in the company's growth and evolution. Prior to the acquisition, he served as Vice President and General Manager of the business. His leadership in Ameresco's core efficiency and infrastructure solutions has been instrumental in the company's long-term success.

With nearly 38 years of industry experience, Mr. Maltezos has a track record of success across a diverse range of roles in engineering, management, and executive positions including an expatriate assignment in Europe. His extensive background encompasses energy savings performance contracting, energy services, distributed generation, mechanical contracting, automation and controls, and utility businesses. Known for his practical and collaborative approach, Mr. Maltezos effectively applies his technical expertise, business acumen, and interpersonal skills to infrastructure modernization and operational excellence to achieve outstanding results. His ability to integrate these skills has been instrumental in advancing Ameresco's mission and fostering a culture of excellence, collaboration, and continuous improvement across the organization.

Mr. Maltezos has been recognized for his leadership and industry expertise, receiving a Gold Globee® Award for Excellence in Strategic Planning at the 2026 Globee Awards for Leadership and a Gold Stevie® Award for Energy Technology Executive of the Year at the third annual Stevie® Awards for Technology Excellence.

He earned an M.B.A. from Northwestern University's Kellogg Graduate School of Management and a B.S. in Electrical Engineering from the University of Illinois Urbana-Champaign.

Joshua Baribeau is Senior Vice President and Chief Investment Officer at Ameresco, a leading energy infrastructure company delivering integrated solutions that create reliable power and modernize infrastructure. He is responsible for leading the company’s capital markets activities, project financings, mergers and acquisitions and related strategic transactions that support Ameresco's growth and delivery of integrated energy infrastructure solutions.

Mr. Baribeau is an accomplished capital markets professional with 20 years’ experience as a financial and business development executive. Since joining Ameresco in 2015, he has served as senior vice president of finance and corporate treasury and the director of new market development. He is a diligent leader with extensive experience overseeing and managing teams that support the company’s investment strategy, project financing, portfolio and risk management, and capital allocation. Mr. Baribeau is a key member of Ameresco’s investor relations team, recognized for delivering high-impact insights to investors, analysts, and portfolio managers regarding the company's infrastructure-focused growth strategy and execution.

Prior to Ameresco, Mr. Baribeau held roles responsible for equity research, investment analysis, and transaction execution at firms including Canaccord Genuity, First Southwest Company, Investors Bank & Trust, and others.

Mr. Baribeau is a CFA Charterholder and earned a Bachelor of Science degree in economics and physics from Boston University.

Alexandra Coleman serves as Senior Vice President, UK Operations Oversight and Special Projects at Ameresco, a leading energy infrastructure company delivering integrated solutions that create reliable power and modernize infrastructure. In this role, she supports the company’s UK operations and strategic initiatives, drawing on extensive experience across energy infrastructure, renewable energy, finance, commercial operations, and business leadership.

Prior to joining Ameresco, Ms. Coleman held a series of leadership positions at Centrica Business Solutions, most recently leading its North American business. During her tenure, she also led the company’s Demand Response and Optimization business and held senior commercial and risk roles spanning commercial operations, investment decisions, project finance relationships, and energy investment underwriting.

Earlier in her career, Ms. Coleman held renewable energy and project finance roles at GE, including investment positions with GE Energy Financial Services and GE Power. Her work included renewable energy equity underwriting and portfolio management across solar, wind, and other renewable energy technologies. She began her career as an engineer with Kiewit Infrastructure Group, serving in multiple project engineering roles on a bridge project in New York City.

Throughout her career, Ms. Coleman has combined engineering, financial, commercial, and operational expertise across the energy sector. She has financed more than $1 billion in large-scale energy projects, with experience spanning construction, renewable energy investment, distributed energy, customer energy solutions, and business leadership.

Ms. Coleman holds an M.B.A. from Babson College and a bachelor’s degree in civil engineering from Bucknell University. She is also a founding board member of Engineering Tomorrow, a nonprofit organization dedicated to inspiring high school students to pursue careers in engineering.

Ms. Leila Dillon is Senior Vice President and Chief Marketing Officer at Ameresco, a leading energy infrastructure company delivering integrated solutions that create reliable power and modernize infrastructure. Ms. Dillon has more than 20 years of experience leading corporate marketing and communications, investor relations, partner strategy, lead generation, and business development initiatives for industry-leading global infrastructure, energy, and technology companies.

In her role, Ms. Dillon leads strategic initiatives that amplify Ameresco's market leadership position, including external communications programs spanning media and public relations, as well as internal communications and employee engagement initiatives. She guides the development of integrated marketing, demand generation, and thought leadership programs that strengthen Ameresco's market presence and support business growth across the organization.

As a key member of the executive leadership team, she helps drive stakeholder engagement, investor relations, and strategic communications initiatives that reinforce Ameresco's vision and positioning among customers, investors, partners, and employees.

Ms. Dillon helped establish Ameresco's ESG Ambassadors program in 2020 as part of a broader commitment to employee engagement and organizational alignment. Through initiatives that connect employees across business units and geographies, she has helped cultivate a One Ameresco culture centered on collaboration, shared values, and a common purpose.

Prior to joining Ameresco, Ms. Dillon served as Vice President of Marketing and North American Distribution for Bigbelly, Inc., a leading provider of Smart City, Internet of Things (IoT), and smart waste management solutions.

A recognized leader in strategic communications, corporate positioning, and stakeholder engagement, Ms. Dillon has helped elevate Ameresco's profile as a leader in energy infrastructure, reliable power, and infrastructure modernization. She is a four-time consecutive honoree in Ragan’s Top Women in Communications Awards, including recognition as a Bridge Builder and Trailblazer for her leadership and impact across business, brand and culture.

Jonathan Mancini serves as Executive Vice President, Solar and Battery Storage Asset Development at Ameresco, a leading energy infrastructure company delivering integrated solutions that create reliable power and modernize infrastructure. In this role, he is responsible for providing leadership and oversight for Ameresco’s portfolio of utility-scale storage and solar assets throughout the United States. He is responsible for asset origination, acquisitions, project engineering, development, construction, and asset management, advancing energy infrastructure projects that support grid reliability, energy resilience, and long-term power needs.

Mr. Mancini is a seasoned energy infrastructure executive with more than 25 years of experience leading the development, permitting, financing, construction, and acquisition of large-scale power generation assets. He has extensive expertise in renewable energy development and infrastructure investment and leads a team focused on delivering utility-scale solar and energy storage projects that help utilities, communities, and commercial customers meet evolving energy demands. Through strategic partnerships with utilities, property owners, industrial customers, and investors, he helps bring complex energy infrastructure projects from concept to operation, creating reliable power and long-term value.

Prior to joining Ameresco, Mr. Mancini held senior roles throughout the renewable energy industry successfully leading teams and organizations to grow their portfolios of renewable energy and energy infrastructure assets.

Mr. Mancini earned a Bachelor of Science degree from the University of Rhode Island in Environmental Management.

Ms. Lenka Patten is Senior Vice President and Chief Human Resources Officer for Ameresco, a leading energy infrastructure company focused on creating reliable power and modernizing infrastructure. Ms. Patten has more than 20 years of forward-thinking human capital experience, bringing a proven track record of implementing integrated human resource strategies that put people first and support the company’s mission, vision, and long-term growth objectives.

In her role, Ms. Patten is responsible for leading the human resources team while supporting the company’s strategic business goals across talent acquisition, professional development, and employee engagement. Joining the company in November 2022, she serves on the executive management team to provide guidance as a personnel advisor to each business unit while cultivating a strong companywide talent strategy and rewarding employee experience that supports Ameresco's continued growth and operational excellence.

Prior to joining Ameresco, Ms. Patten served as the head of human resources for Reebok International, where she was responsible for developing and executing global human resource strategy, specifically in the areas of talent management; diversity, equity and inclusion; organization design; performance management; training and development; social purpose and community impact, among others. She’s also held human resources leadership roles at other organizations, including Fidelity Investments and publicly traded State Street Corporation.

Ms. Patten graduated from the University of Economics in Prague, Czech Republic with a bachelor’s degree in economics and comparative politics and a master’s degree in economics. She also holds a master’s degree in organizational development from American University in Washington, D.C. and is a Society for Human Resource Management Senior Certified Professional, a nationally lauded recognition.