The main purpose of this legislation is to update and improve energy efficiency standards for certain heating and cooling appliances, specifically furnaces, central air conditioners, and heat pumps. The goal is to ensure that these appliances are more energy-efficient, which can help reduce energy consumption and lower utility bills for consumers. One of the key provisions of the legislation is a change in how energy efficiency standards are applied. Previously, the standards were set to apply only to products that were installed after a certain date in specific states.