Energy efficiency is often referred to as the best, cheapest and the least environmentally damaging source of energy supply. To prove this statement, the comparison of energy saving costs and costs of energy produced from new generating capacities has been performed. The results confirm energy efficiency as the most feasible energy supply option, which can significantly contribute to the improvement of the overall energy supply security in a country. However, despite these benefits and policy recognition of energy efficiency, vast potential of this new energy source, often referred as "negajoules", is still untapped. The main reason behind this policy failure is only declarative and not real political commitment and a complete lack of focus on implementing capacities that would ensure full policy uptake.