Abstract
From the viewpoint of economical illumination, The costs of luminares, ballasts, lamps and their watt losses are substituted by the function of initial luminous flux Fo, and so, the experimental formulas are introduced nearly; Example the costs of fluorescent luminaires and ballasts CFF+CBF=αFFo+βF, CFF+CBF (yen), coefficients αF=0.85 and βF=1.22×103etc.
On the other hand, the mean luminous flux in, burning time of their light sources are simplified by the experimental formulas of ratio of mean flux per initial flux and burning flux per initial flux. The author discussed the general tendency of economical lamp lifes, total anual costs and initial installation costs including lamps by initial flux or economical flux using the experimental formulas.
