Lighting Research and Technology vol:39 issue:2 pages:171-184
This paper concentrates on the formulation of a general criterion for the assessment of the power installed for lighting to achieve adequate illuminance under night-time conditions. Actual efficiency criteria are formulated in terms of the normalized power density. Target values are based on current good practice, assuming a standard task area more or less equal to the floor area of the room. European Standard EN12464 "Lighting of work places", however, defines specific task areas and task illuminances. A general criterion for the assessment of the energy efficiency of a lighting installation which is broadly applicable and easy to use is developed, taking into account lighting comfort requirements. An analytic expression for the utilance target value is presented.