Which energy metric is used to determine energy performance of ENERGY STAR for Homes?

The HERS Index is the correct metric for evaluating the energy performance of ENERGY STAR for Homes. The Home Energy Rating System (HERS) Index measures a home's energy efficiency on a scale, with lower scores indicating greater energy efficiency. It is a standardized means of assessing a house's energy performance, allowing for the comparison of energy efficiency across different homes.

This index takes into account various aspects of a home's design, such as insulation, windows, heating and cooling systems, and other factors that affect energy consumption. As such, builders and homeowners can use the HERS score to understand their home's energy performance relative to the national scale, guiding improvements and compliance with ENERGY STAR standards.

The other choices, while relevant to energy performance in different contexts, do not pertain specifically to ENERGY STAR for Homes. For example, the ASHRAE Score is used in commercial buildings but is less applicable in residential energy rating. The SEER Rating measures the efficiency of cooling systems but doesn't provide a comprehensive evaluation of an entire home's energy use. The Energy Star Score pertains to ENERGY STAR certified products and buildings but is not as specifically linked to the residential energy performance assessment as the HERS Index is.