Two NatHERS Ratings Explained
The NatHERS thermal star rating and Whole of Home rating measure different parts of residential energy performance. One assesses the thermal response of the building shell. The other assesses major household energy uses, onsite generation and storage.
NatHERS and Whole of Home are sometimes described as competing assessment methods. This is no longer an accurate way to understand their relationship.
NatHERS is the wider residential energy-rating framework. Within that framework, a proposed home can receive a thermal star rating out of 10 and a separate Whole of Home rating out of 100. The two results answer different questions about the same dwelling.
The thermal star rating asks how much heating and cooling the home is likely to need because of its design and construction. The Whole of Home rating builds on those thermal loads and considers the energy performance of household systems, solar generation and battery storage.
