When making large purchases like an air conditioning unit, the difference in price between units can often deter consumers from selecting higher-end, more expensive units. However, the conscious consumer should recognize that the question is not which unit is cheaper up front, but instead which unit will cost the least over the lifetime of the unit. Consider a dwelling that does not require air conditioning 25% of the year ( 365 days). When the dwelling does require AC, it receives heat from the surrounding environment at an average rate of Q ˙ ​ env ​ =20 kW. There are also people and appliances in the home that generate energy at an average rate of Q˙ gen ​ =1 kW. Create a schematic of the dwelling and the air conditioning unit. Clearly identify any energy interactions between the dwelling and the surroundings, the dwelling and the AC unit, and the AC unit and the surroundings.