RETScreen provides amazing, and free, tools for fiscal, GHG and lifecycle evaluation of renewable energy projects. They provide excel worksheets, instructions, case studies, textbooks, etc. and they do it in 30 languages.
The RETScreen International Clean Energy Project Analysis Software is a unique decision support tool developed with the contribution of numerous experts from government, industry, and academia. The software, provided free-of-charge, can be used worldwide to evaluate the energy production and savings, life-cycle costs, emission reductions, financial viability and risk for various types of energy efficient and renewable energy technologies (RETs). The software also includes product, cost and climate databases, and a detailed online user manual.