We have three different bulbs. The first bulb is the LED bulb. The energy use of one LED is 9 watts (0.009 kWh). The lifespan of one LED bulb is 25,000 hours. The second bulb is the CFL bulb. The energy use of one CFL is 23 watts (0.023 kWh). The lifespan of one CFL bulb is 12,000 hours. The third bulb is the incandescent light bulb. The energy use of the incandescent light bulb is 60 watts (0.06 kWh). The average use per day is 5 hours. The estimated number of light bulbs per house is 20 light bulbs per house. The price of electricity in Hoboken is $0.15/kWh. The average use per day, the estimated number of light bulbs per house, and the price of electricity is the same across all three bulbs.

Preparation question 5: How much energy is consumed by 20 LED bulbs used for five hours per day for a year (expressed in kWh/year per house)? A year consists of 365 days. ________W 1000 W/kWh = _______ kWh ________kWh x 5h/day = _______kWh/day ________kWh/day x 365 days = _________kWh/year ________kWh/year x 20 incandescent bulbs per house = _______kWh/year per house

What is the annual cost of using 20 LED bulbs used for five hours per day for a year? A year consists of 365 days (expressed in $/year). _______kWh/year per house x $0.15/kWh = $_______/year