Due to constant increase in energy consumption, impacts on the environment are already showing. Since buildings consume a large part of all energy produced, there is a huge need for reducing energy demands. The main idea behind a low-energy house is that it is designed to consume as little energy as possible and is equipped with modern technologies in such a way that it covers most of its energy needs to meet the set standards. In the final thesis, we will define different types of low-energy buildings in regard to amount of consumed energy and different continent (the EU and the USA). Definitions between different countries or continents do not differ significantly, but it is true that every country has its own characteristics. It is also important that the investment costs are not too high and that the input is repaid within a certain period. Evaluation of low-energy buildings, complexes or neighborhoods is a complicated process and leaves many unanswered questions for the future, as there is no common system for evaluation of non-renewable energy.