To calculate total annual costs per illumination levels the formulas of mean illumination levels Em in burning time on the lighting installations where are given depreciation curves of mean illumination levels in luance of luminaires and room surfaces including performance of light sources, are introduced nearly.
E_m⇔E₀(1-G)+E₀G/2{_gT-(_gT2)²/2+(_gT)³/6}
where E_o: initial illumination levels (lx) T: burning times per 100 (hr) G and g: coefficents
examrples G₁=0.48 and g₁=0.023 on low bay office
G₂=0.69 and g₂=0.022 on high bay heavy shop
On the other hand the author searched economical illumination levels on industrial, office and street lightings and discussed that their economical illumination levels are effected by a ratio of fixed charges per costs of lighting and the ratio increases the more their economical illumination levels increase themore.
There fore, the cost of production must be recreased which increases illumination levels and operates installations usefully when lighting installations are very expensive. and so, economical illumination levels are not equal by differ costs of light if fixed charges constant in equal fluorescent lamp or fluorescent merury lamp instations.

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