To meet Most Efficient Criteria AND be eligible for federal tax credits:

1) Product must be ENERGY STAR® certified consistent with applicable ENERGY STAR Partner Commitments. The ENERGY STAR 7.0 Product performance
(U-factor and SHGC) must be certified by an EPA-recognized certification body.

2) Product must be independently certified to meet the North American Fenestration Standard/Specification (NAFS) with a Performance Grade ≥ 15. Acceptable certification bodies shall be accredited to operate in accordance with ISO/IEC 17065 by an accrediting body that is a signatory to the International Accreditation Forum Multilateral Recognition Agreement. NAFS certification does not require an EPA-recognized certification body.

3) Product must meet these applicable requirements:

 Starting in 2023, only windows that meet ENERGY STAR Most Efficient criteria are eligible for federal tax credits.