Traffic lights are being converted from incandescent bulbs to LED arrays to save operating and maintenance costs.

Typically each incandescent light uses three 100-W bulbs, one for each color R, Y, G. A competing LED array consists of 61 LEDs with each LED requiring 9 V and drawing 20mA of current. There are three arrays per light – R, Y, G.Asmall city has 1560 traffic signals. Since one light is always on 24/7, how much can a city save in one year if the city buys their electricity at 7.2c= per kWh?

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