Sources & credits

Data

• ENERGY STAR Certified Heat Pumps

  U.S. Environmental Protection Agency. Every outdoor unit, indoor unit, pair, rating and AHRI reference number in the lookup. A work of the U.S. federal government; re-imported weekly. Certification figures are submitted by the manufacturers to EPA.

• HVAC Design Manual, Table 7-1 “Climatic Conditions”

  U.S. Department of Veterans Affairs, Office of Construction & Facilities Management. November 1, 2017, revised March 1, 2024. The design temperatures for 169 cities. A work of the U.S. federal government.

• Federal rules cited in the field guide

  Each field guide page lists its own sources — the Code of Federal Regulations, the Federal Register, EPA and the Department of Energy — next to the figures it reports, with the date they were checked.

Drawings

The 16 technical diagrams, the icons and the maps were drawn for this site. They are not taken from a textbook, a standard or a manufacturer’s literature.

Brand names

Manufacturer and model names appear only to identify the equipment they belong to. A2L Crosswalk is independent: it is not affiliated with, sponsored by or endorsed by any manufacturer, by AHRI, by EPA or by the ENERGY STAR program. No manufacturer logo or product photograph is used.

Photographs

• 
  A residential outdoor unit on a concrete pad beside a house with green siding, with its electrical disconnect on the wall

  Credit: NIST · Public domain (U.S. Government work) · source
• 
  A technician’s hands holding a manifold gauge set connected to an R-410A charging hose

  Photo by José Andrés Pacheco Cortes on Pexels (cropped) · Pexels License · source
• 
  The outdoor unit of a ductless mini-split on a balcony, with its disconnect on the wall

  Photo by Wikideas1, CC0 (cropped) · CC0 1.0 Universal (public domain dedication) · source

Photographs are illustrative. Equipment shown is not an endorsement of or by any manufacturer.