Celtic Energy's clients include:

Corporate

• ADT Construction Group
• American Continental Properties, Inc.
• Dominion Project Management, Inc.
• Hartford Insurance
• Hispanic Health Council
• ISO New England
• Kerite Company
• Jones Lang LaSalle
• LMGA Consulting Engineers
• Lutron, Inc.
• Mass Mutual Financial Group
• NCR Corporation
• New York Presbyterian Hospital
• SLAM Collaborative
• Travelers Insurance
• Trammell Crow Corporate Services, Inc.
• William Beaumont Hospital

Celtic Energy's past clients include:

Corporate

• Aetna Insurance
• Bell Atlantic (Now dba Verizon)
• Cadbury-Schweppes
• Chesebrough-Ponds
• CIGNA
• Dresser-Rand Industries
• Eli Lilly
• GE Plastics
• GTE
• Hartford Insurance
• Kimberly Clark
• Kraft
• IBM
• Jones Lang LaSalle
• Pfizer Pharmaceuticals
• Phoenix Life Insurance
• Procter & Gamble
• Travelers Insurance
• Union Carbide
• Xerox

Government

• US Department of Energy
• National Renewable Energy Laboratories
• State of Connecticut DPW
• State of Nevada Purchasing Div.
• Nevada Department of Human Resources
• United States Postal Service
• US Bureau of Prisons
• US Internal Revenue Service
• Nellis AFB, Las Vegas NV
• Fort Drum, NY
• City of Derby, CT
• City of Henderson, NV

Government

• City of West Haven, CT
• State of Connecticut DPW/OPM
• State of Massachusetts Dept of Energy Resources
• State of New York Energy Office
• State of Maryland Energy Office
• State of Florida Energy Office
• US Army
• US Department of Energy
• US Postal Service
• City of Riviera Beach, FL
• Fort Benning, GA
• Natick Soldier Systems Command, MA
• US Dept of Health and Human Services -Indian Health Service Fort Jackson, SC
• Carl Stokes Federal Courthouse Town of Windham, CT

Educational

• Clark County School District, NV
• Norwalk Community College
• University of Connecticut
• Storrs Campus
• West Hartford Campus
• School of Law
• Torrington Campus
• New London, CT School System

Educational

• Over 40 Florida School Districts
• Hamilton College
• Longwood College
• Northern Virginia Community College
• Towson State University
• University of Massachusetts- Amherst

Utilities

• Connecticut Light & Power
• United Illuminating
• National Grid USA
• NSTAR Electric & Gas

Utilities

• Boston Edison Company
• Central Maine Power
• CINergy/PSI
• Commonwealth Edison
• Connecticut Light & Power
• Consolidated Edison of New York
• Green Mountain Power of VT
• Niagara Mohawk Power

Health Care

• Brigham & Women’s Hospital
• JFK Medical Center
• US Veterans Administration Hospitals- VISN 1 - New England