Keeping your cool - A multi-stakeholder look at AC sizing

Selecting the capacity of a central air conditioning (AC) system is based on a long list of structural factors within a home, but is normally chosen without considering effects on stakeholders outside of the home. Energy use by residential air conditioners is relevant to consumers as an expense, but also to utilities as a contributor to peak demand and to society by the resultant emissions. In this article, we investigate how size and operational patterns of central residential air conditioners interact with stakeholder benefits and costs. The case study analyzes energy use for systems sized from 3.0 to 5.5 tons in single family homes in Phoenix, Arizona and quantifies the costs and benefits to homeowners, electric utilities, and society. For homeowners, larger systems are preferred due to lower energy consumption, leading to lower net costs, and the ability to cool the house quickly. However, under the same conditions, a smaller AC system provides double the potential profit to the utility from reduced generation and peak load costs. Because of lower energy consumption, larger systems have lower environmental externality costs from carbon and criteria pollutant emissions. However, a social perspective that considers homeowner, utility and externality costs together results in an overall preference for smaller systems with setback schedules, driven by the value of peak demand reduction.