Best Energy Companies in Connecticut, United States
The 126 best Energy companies in Connecticut, United States in 2026, ranked by funding and momentum. Funding, investors, founders, valuation, tech stack and live signals. Top: Avangrid.
Our analysis of 171 Energy companies
$71.4b in tracked funding; 82% of the stack-profiled cohort runs cloud-native; funding activity peaked in 2025.
Ranked: Best Energy companies in Connecticut
| # | Company | Last round | Disclosed funding | Employees | Founded | Founder | Patents & IP focus | Recent signals |
|---|---|---|---|---|---|---|---|---|
| 1 | Advanced Fuel Research Firm engaged in research on advanced fuel | — | — | 8 | 1980 | James R Markham CEO | — | — |
| 2 | AIMCOR Provider of transport & selling petroleum and refining services | — | — | — | 1996 | William Koch CEO | — | — |
| 3 | air temp mechanical services Air-Temp Mechanical offers mechanical systems design, installation, and service for commercial or industrial… | — | — | 50 | 2001 | Jeff Leone CEO | — | — |
| 4 | alloy specialties Alloy Specialties is a manufacturer of engine components for defense and commercial air and ground… | — | — | 39 | 1980 | — | — | — |
| 5 | AltEnergy Developer of electricity transmission based utility projects | — | — | 3 | 2021 | — | — | — |
| 6 | Alteris Renewables Developer of solar and wind energy projects | — | — | 1 | 1980 | — | — | — |
| 7 | American Energy Group Developer of connected devices and software solutions for enterprise value creation | — | — | 16 | 2003 | — | 128 patents Advanced safety and control components for rechargeable metal‑ion batteries. | — |
| 8 | american greenfuels American GreenFuels is a manufacturer of biodiesel. | — | — | 8 42 → 33 (-21%) | 2004 | — | — | — |
Top 12 Energy companies in Connecticut
#1
Funding Raised · Stamford, Connecticut · founded 2018 · 50 employees$1.8Braised▾
Provider of oil & gas downstream services
- Nov 2024Conventional Debt$800M
- Sep 2022Conventional Debt$205M
- Oct 2021Conventional Debt$540M
- Nov 2019Conventional Debt$175M
#2
Series B · Greenwich, Connecticut · founded 2017 · 3 employees$2.1Mraised▾
Provides affordable energy storage solutions
- Nov 2025Series B$4.6M
- Mar 2024Series A$4.4M
- May 2022Seed$2M
- Aug 2020Seed$40.8K
#3
Funding Raised · Bozrah, Connecticut · founded 1995 · 201 employees$4Mraised▾
Soybean processor and biodiesel manufacturer. This company processes soybeans to produce soybean oil, biodiesel, and high-protein animal feed. The refined, bleached, and deodorized soybean oil is packaged and available for private labeling. Biodiesel production meets BQ-9000 and RFS certification standards. The company's product line caters to various industrial and consumer needs.
- Feb 2025Grant (prize money)$288.4K
- Sep 2011Grant (prize money)$1.7M
- Sep 2011Grant (prize money)$1.8M
- Dec 2010Grant (prize money)$205.4K
#4
Acquired · Orange, Connecticut · founded 2015$2.5Braised▾
Provider of electricity and natural gas to homes and businesses. This company operates a network of utilities, delivering energy to consumers. It also invests in renewable energy sources such as onshore and offshore wind. The organization has a focus on sustainability initiatives, including climate action and decarbonization efforts. Internal operations include a robust compliance program and corporate governance structure. The company supports employee development and offers various programs for supplier engagement.
- Jul 2018Conventional Debt$2.5B
#5
Acquired · Glastonbury, Connecticut · founded 2006$97.5Mraised▾
Developer of clean energy solutions and hydroelectric power projects. It develops and operates hydroelectric power facilities, contributing to the transition to a clean energy economy. The company also manages significant land and water resources, providing recreational opportunities. Its focus is on engineering, development, and operation of sustainable energy infrastructure. It actively engages with communities and stakeholders.
- May 2023Conventional Debt$97.5M
#6
Public · Stamford, Connecticut · founded 2002 · 593 employees$518Mraised▾
Liquefied natural gas logistics management services
- Feb 2014Post IPO$100M
- Nov 2013Post IPO$250M
- Jul 2013Post IPO$168M
- Oct 2010Seed—
#7
Acquired · Middletown, Connecticut · founded 2008 · 83 employees$247Mraised▾
Vertically-integrated solar energy solutions provider for commercial, public sector, and utility clients. The company offers comprehensive decarbonization solutions, including onsite and offsite solar, battery storage, microgrids, and combined cooling, heating, and power. They originate, develop, construct, and operate renewable energy facilities. The company provides project financing, operations and maintenance, project acquisition, and co-development services. They cater to landowners, building owners, commercial and industrial entities, municipalities and schools, nonprofits, universities, and hospitals. Their offerings include solar plus new roof options, parking lot solar installations, utility-scale projects, and community solar programs. They focus on environmental, social, and governance goals, providing clean energy solutions and promoting sustainability.
- Jan 2020PE—
- Aug 2015Conventional Debt$165M
- Jul 2014Conventional Debt$82M
#8
Series D · Wallingford, Connecticut · founded 1996$114Mraised▾
Process optimization solutions provider and product developer. Provides process optimisation and enhanced recovery services for natural resources. The company has developed various service offerings related to flow management and assurance, overall plant monitoring and process optimisation in the natural resource industries including mining, oilsands, power generation, chemical management and pulp and paper applications.
- Dec 2020Series D—
- Aug 2011Series D$10M
- May 2009Series D$4M
- Jun 2000Series D$100M
#9
Seed · Greenwich, Connecticut · founded 2022 · 8 employees$500Kraised▾
Stardust Power, Inc. is strategically developing a vertically integrated lithium refinery in the United States with the capacity to produce 50,000 tons per annum of battery-grade lithium. The company aims to supply the EV industry and contribute to America's energy independence.
- Oct 2024Seed$500K
#10
Public · Stamford, Connecticut · founded 1991 · 270 employees$38.9Mraised▾
Revolution Lighting Technologies engages in the design, manufacture, marketing, and sale of light emitting diode (LED) lighting. The company goes to market through its Seesmart brand, which designs, engineers and manufactures an extensive line of high-quality interior and exterior LED lamps and fixtures, Lighting Integration Technologies which sells and installs Seesmart products, Lumificient, which supplies LED illumination for the signage industry, Relume Technologies, a leading manufacturer of outdoor LED products; and Sentinel, a revolutionary patented and licensed monitoring and smart grid control system for outdoor lighting applications. It markets and distributes its product through a network of independent sales representatives and distributors
- Dec 2016Post IPO$9M
- Aug 2013Post IPO$15M
- Jun 2009Post IPO$3.8M
- Nov 2008Post IPO$7.6M
#11
Public · Enfield, Connecticut · founded 1944 · 63 employees$21.7Mraised▾
Solar panel encapsulation leader, providing environmentally-responsible solutions through research and innovation. The company is dedicated to advancing renewable energy through scientific breakthroughs in solar encapsulation. With a history rooted in the development of EVA-based solar encapsulants, the company demonstrates a long-standing commitment to the solar industry. The company focuses on continual research, development, and innovation to provide its customers with environmentally responsible solutions. This makes them a key player in the renewable energy sector, contributing to a more sustainable future through advanced materials and technologies. The company's work directly supports the growth and efficiency of solar energy adoption worldwide, making it a business with a significant positive social impact.
- Aug 2014PE$21.7M
- Sep 2005Conventional Debt—
#12
Acquired · Windsor, Connecticut · founded 1969 · 4367 employees$15.5Mraised▾
Provider of engineering and construction management services to multiple industries such as power and utilities, real estate, water, wastewater, etc.
- Sep 2011Grant (prize money)$200K
- Jun 2009Series B$15.5M
Funding & investor landscape
Notable founders
Market landscape — 10 sub-themes by coverage
Share of Energy coverage by sub-theme.
Regulatory-risk over time rising
Funding & growth over time
funding rising · growth rising
What Connecticut researches in energy storage
University of Connecticut dominates Connecticut's energy-storage research, focusing on microgrids and dielectric materials, with 19 recent papers reflecting strongly optimistic momentum toward practical breakthroughs.
- University of Connecticut20
Common questions
Riya reads income statements for fun. She covers the real money in a sector — revenue, growth, who actually earns — and never met a vague claim she didn't want a number for.