GT Consulting's clients have included private companies, other consulting firms, non-governmental organizations, government laboratories, bilateral agencies, and multilateral development institutions, including:

Argentina (Government)
Arthur D. Little
Biomass Users Network, Central America (BUN-CA)
Centro de Estudios Urbanos y Regionales, Dom. Rep. E+Co
Ecuador (Government), Ministry of Mines and Energy
Environmental Enterprises Assistance Fund
IHRDC
International Finance Corporation
McKinsey & Co.
National Renewable Energy Laboratory
Sandia National Laboratories
Solar Development Group
SunLight Power International
Sunrise Technologies Consulting/REPP
Winrock International/USAID
World Bank (IBRD)