A new home must be built to ERS standards.

For an existing home, a comprehensive HERS home energy rating, conducted by a certified Home Energy Rater, is the most in-depth energy performance assessment of a home that you'll find. It consists of diagnostic testing using specialized equipment, such as a blower door test, duct leakage tester, combustion analyzer and infrared cameras to determine:
• The amount and location of air leaks in the building envelope
• The amount of leakage from HVAC distribution ducts
• The effectiveness of insulation inside walls and ceilings
• Any existing or potential combustion safety issues
Other variables that are taken into account include:
• Floors over unconditioned spaces (like garages or cellars)
• Attics, foundations and crawlspaces
• Windows and doors, vents and ductwork
• Water heating system and thermostats
The comprehensive HERS rating provides a computerized simulation analysis utilizing Accredited Rating Software to calculate a rating score on the HERS Index. The report can also contain a cost/benefit analysis for the recommended improvements and expected return on investment.