ABSTRACT
Lighting energy constitutes 25–50 per cent of the total electricity used in commercial buildings in OECD countries, and so is an important area for energy conservation. The first strategy with regard to lighting in buildings should be to design the building to make maximum use of natural sunlight, subject to the various other constraints that must be satisfied. This strategy should be complemented by the design of a complementary electric lighting system that provides supplementary light only where it is needed, when it is needed, and in the quantities needed. The third strategy is to choose the most efficient individual components for use in an efficiently designed system. In this way, large (50–90 per cent) reductions in lighting energy use can be achieved in new buildings and frequently in retrofits of existing buildings, particularly when the baseline condition involves lighting in office buildings turned on 24 hours per day, as is often the case in North America. In residential buildings, the role of lighting is much less, but large efficiency gains are easier to achieve.
