The HERS (Home Energy Rating System) Index is a 0-150 scale measuring a home's overall energy efficiency, developed by RESNET. Lower numbers mean more efficient: a HERS 100 score represents a "standard new home" built to model energy code; HERS 0 represents net-zero energy use; HERS 130+ represents a very inefficient home.
HERS ratings are most commonly used in new construction (some jurisdictions require a HERS score for the certificate of occupancy) and in green-building certifications. For existing homes, HERS ratings are voluntary and produced by a certified HERS Rater.
An HVAC equipment upgrade typically improves a home's HERS score by 5-15 points, depending on the efficiency delta between old and new equipment.
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