The greenhouse gas return on investment (GROI) metric is introduced as a compliment to the energy return on investment (EROI). Unlike EROI, GROI accounts for the life cycle energy mix, the efficiency, circularity, and supply chain of energy distribution, and the energy offset by a new energy installation. The average greenhouse gas emissions of labor and electricity are calculated for multiple countries to be used in GROI calculations. GROI is applied to a case study of SolFocus Inc. solar panels, and the potential extension of GROI methodology to a modified EROI and to decision making beyond energy is discussed.

Life-cycle assessment (LCA) is utilized to analyze SolFocus Inc. concentrator solar systems. A hybrid LCA methodology is explained that combines process and input-output LCA techniques. The use of the greenhouse gas return on investment metric for solar technologies is discussed as a complement to energy metrics. Finally, preliminary results of a hybrid LCA for the SolFocus concentrator technology are presented. It is found that transportation and electricity consumption play a significant role in energy consumption and greenhouse gas emissions.

A supply-chain decision tool is outlined that will assess the life-cycle greenhouse gases and energy demand of solar energy technology using a hybrid LCA structure. Energy and greenhouse gas metrics appropriate for the climate change mitigation goals of solar energy are discussed. Applying this methodology to SolFocus Inc. concentrator systems, preliminary results indicate that the energy payback time of SolFocus Panels can vary from 0.6 to 5 years depending on manufacturing locations. The greenhouse gas payback time, a new metric for energy technologies, varies from 1.1 to 64 years depending on the same factors indicating that greenhouse gas metrics are more sensitive to installation and supply chain decisions than energy metrics.