Does an ADU Need HERS Registration?

It depends on the measures the design relies on. Where any of them require field verification, the compliance forms are registered with an ECC provider and a rater has to verify the work on site.

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What registration means

Some Energy Code measures cannot be certified on paper alone — they have to be tested or inspected in the finished building. Where a design relies on one of those, the compliance documents are not simply printed and signed. They are completed through an approved data registry operated by an approved provider, and the registry issues them with a registration number that ties the paperwork to the project.

You will still see this called HERS registration, and that is what it was called until 1 January 2026. On that date the field verification and diagnostic testing side of the HERS Program moved into the new Energy Code Compliance (ECC) Program: HERS Providers became ECC-Providers and HERS raters became ECC-Raters. The tests did not change and neither did what you have to do — the programme, the registries and the job titles were renamed. The HERS Program still exists, but its scope is now whole-house ratings and home energy audits, which no longer demonstrate Title 24 compliance.

Who does what

The design-stage certificate identifies which measures will need verification. During construction, the installing contractors complete their Certificates of Installation. A third-party rater then carries out the tests and completes the Certificate of Verification, and the result is reported to the registry as a pass or a fail. A failed verification has to be corrected and re-verified; it is not a paperwork formality.

When an ADU avoids it

Not every ADU has the same verification list. A ductless heat pump skips the tests that apply only to ducted systems, such as duct leakage and fan efficacy, so the list is shorter. It does not usually remove the rater: the Energy Commission's ADU guidance says mini-splits and multi-splits may still need ECC-Rater field verification and diagnostic testing, depending on the scope of the project. That is a design decision as much as a compliance one, and it is worth taking deliberately: choosing a system with a shorter list removes work from the end of the build, and reading the list before you choose avoids a surprise at final.

Where verification is unavoidable, the thing that causes trouble is discovering it late. A rater has to be engaged and the tests scheduled before the building is closed up and signed off, so the requirement is better identified at design stage than at final inspection.

Common Title 24 Questions

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