a. Estimate the annual energy cost of DHW heating for an office building occupied by 1,000 people. Each person uses on average 3 gallons per day of hot water. The water temperature at the bathroom sink is 120°F. Due to the length of the distribution system, an average of 20°F decrease in water temperature occurs before the hot water reaches the bathroom sink. The heater is an oil-fired boiler with an efficiency of 75 percent. The cost of fuel is $1.20/gallon. Assume that the entering water temperature is 55°F and that the building is occupied 300 days per year.

b. Determine the cost savings if the losses in hot water temperature in the distribution system are virtually eliminated by insulating the pipes.