Energy efficiency (EE) is, maybe, the most important thing for building sustainable future, especially combined with using renewable energy sources. EE means using modern technologies, which are already available, to create products and processes that use less energy. Basically, it is the way of improving energy consumption in products that are daily used and in processes in industry. Using EE has two goals: decrease of energy usage and, as a result, less price to pay for energy. Main problem with implementing EE is that it requires investment up front, and results are becoming visible in the future. For example, insulating a house will return investment with energy savings in about 3-6 years, depending on situation, house size, fuel used for heating, needs for cooling etc. European Union is using different types of stimulation for EE: tax returns, subsidies, smaller interest rates when applying for EE credit etc.