Criteria for energy efficient lighting in buildings

In order to assess the energy efficiency of an indoor lighting installation, a criterion for the installed electrical power is proposed which is broadly applicable and easy to use. Introducing target values for lamps and gear and taking into account some basic lighting comfort requirements, the maximum electrical power to be installed can be predicted for any kind of application. Herewith, one or more task areas with appropriate target illuminance values may be defined. The key parameter of the criterion is the analytical expression for the target utilance as a function of common lighting design parameters.Two practical examples illustrate the validity of the criterion. In a first example, a general case where the task area is coincident with a reference plane parallel with the floor has been studied. The values obtained converge to actual target values in current practice. In a second example, the lighting design of a store with many vertical task areas is explained. These cases illustrate the advantages of the criterion as compared to energy evaluation criteria based on the normalized power density.From 2010 on, the proposed criterion will be used in Flanders to assign grants for a re- or newlighting.