Consider a ranch house of 100 m2 located in Phoenix, CO, with a total window area of 15 m2 with double-pane glazing that has a visible transmittance of 0.35. The home has 20 incandescent lamps, each rated at 60 W.

(a) Estimate the energy use and cost savings when the incandescent lamps are replaced with 13 W CFLs

(b) Determine the energy use and cost savings due to daylighting harvesting strategies for both options with the existing incandescent lamps and with CFLs. Assume that without daylighting harvesting, each lamp is operated 4 h/day when daylighting can be harvested, 6 days/week, 50 weeks/year. The cost of electricity is 0.12/kWh.