The aim of this thesis was to find the best investment calculation method for evaluating green energy investments. The study was implemented by the literature review of different investment calculations. The three investment calculation methods selected for the study were net present value (NPV), internal rate of return (IRR) and benefit-cost ratio (BCR).

Investment calculations were based on a real, implemented energy efficiency project for two office buildings in Espoo. The selected investment calculation methods were used for evaluating the profitability of the project. Sensitivity analyzes were carried out and included to the study.

By using all the selected investment calculation methods the green energy investment was profitable. Some of the methods were better in use than the others, but all the methods will find their own uses in the future when the company owner carries out following green en-ergy and other possible investments.