Methodological Guidelines on Net Energy Analysis of Photovoltaic Electricity

Net Energy Analysis (NEA) is a structured, comprehensive method of quantifying the extent to which a given energy source is able to provide a net energy gain (i.e., an energy surplus) to the end user, after accounting for all the energy losses occurring along the chain of processes that are required to exploit it (i.e., for its extraction, processing and transformation into a usable energy carrier, and delivery to the end user), as well as for all the additional energy ‘investments’ that are required in order to carry out the same chain of processes. However, this general framework leaves the individual practitioner with a range of choices that can affect the results and thus, the conclusions of a NEA study. The current IEA PVPS guidelines were developed to provide guidance on assuring consistency, balance, and quality to enhance the credibility and reliability of the results from photovoltaic (PV) NEAs. The guidelines represent a consensus among the authors ‐ PV NEA experts in North America, Europe, and Asia ‐ for assumptions made on PV performance, process inputs and outputs, methods of analysis, and reporting of the results.

Guidance is given on photovoltaic‐specific parameters used as inputs in NEA and on choices and assumptions in inventory data analysis and on implementation of modelling approaches. A consistent approach towards system modelling, the functional unit, the system boundaries and allocation aspects enhances the credibility of PV electricity NEA studies and enables balanced NEA‐based comparisons of different electricity producing technologies. This document provides an in‐depth discussion of a common metric of NEA, namely the energy return on investment (EROI), and how this is to be interpreted vis‐à‐vis the deceptively similar‐sounding metrics in the field of Life Cycle Assessment (LCA): cumulative energy demand (CED) and non‐renewable cumulative energy demand (nr‐CED) per unit output.