Wikipedia
The RETScreen Clean Energy Management Software (usually shortened to RETScreen) is a free clean energy software package developed by the Government of Canada that includes RETScreen Version 4 and RETScreen Plus.
RETScreen 4 is a Excel-based clean energy project analysis software tool that helps decision makers determine the technical and financial viability of potential renewable energy, energy efficiency and cogeneration (combined heat & power) projects. Conventional energy projects can also be modeled and compared to cleaner alternatives. Users conduct a five step analysis, including energy analysis, cost analysis, emission analysis, financial analysis, and sensitivity/risk analysis.
RETScreen Plus is a Windows-based energy management software tool that allows project owners to verify the ongoing energy performance of their facilities.
RETScreen Expert, currently under development, is an advanced new version of the RETScreen software and is expected to allow users to evaluate energy investments over an entire project life-cycle (including benchmarking, feasibility and performance analysis) in a fully integrated fashion, and within one software platform.
The software integrates a number of databases to assist the user, including a global database of climatic conditions obtained from 6,700 ground-based stations and NASA's satellite data; benchmark database; project database; hydrology database and product database. The software also includes clean energy policy & legal toolkits, as well as a large amount of multilingual and multimedia free training material, including an electronic textbook.