A. During a lighting survey you discover thirty-six 250-Watt mercury vapor cobra

Question

A. During a lighting survey you discover thirty-six 250-Watt mercury vapor cobrahead streetlights operating 4300 hours per year on photocells. How much can you save by replacing these fixtures with 70-Watt HPS cutoff luminaires? There is no demand charge, and energy costs $0.055 per kWh. Assume both lamp lives are about the same. Assume both lamp costs are about the same. B. My office light has louvers bottom enclosure and opaque with 15% or more up light through apertures. Find the maintenance schedule if the ambient dirt is almost negligible? I am wining to wait until the light intensity drops to 90% of the full brightness.

Explanation / Answer

36 no.s of 250W will consume = 36*250 W = 9000W of energy

36no.s of 70W luminaires will consume = 36*70 = 2520W of energy

In a year, with 4300 hours of operation, the saving would be = (9000-2520) * 4300 = 27864 * 103Wh = 27864 kWh

Thus the total saving would be = 27864 * 0.055 = 1532 USD

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