Design and energy performance assessment of high-efficiency lighting systems Indoor lighting efficiency is a major opportunity for energy efficiency in buildings, towards near zero energy buildings. In addition to increasing lamp efficacy, lighting design has evolved from a “night-time” approach to a “day-time approach”, taking advantage of control equipment and strategies and of daylight contribution. To date, lighting efficiency is committed to the designer’s skill, while an aided design tool could allow for a real-time efficient design. In this work, evaluation procedures are reviewed and a design tool is devised. A set of case studies is then evaluated, returning reference values and comments for an efficient lighting design. An efficient lighting system is then proposed, according to design comments. In conclusion, a real-time design aid can be a useful tool for efficient lighting design.