Glossary · Safety and certification

What Is an NRTL? Nationally Recognized Testing Laboratories

NRTLNationally Recognized Testing Laboratory

A private lab that OSHA recognizes as qualified to test products and certify they meet safety standards. UL, CSA Group and Intertek are examples.

  1. OSHA sets its rules for nationally recognized testing laboratories
  2. The first organization is recognized as an NRTL
  3. UL Solutions, an NRTL, opens UL 3700 certification for plug-in solar
  4. OSHA's current list shows 21 recognized organizations
From OSHA's lab rules to the first plug-in solar certification program.

At a glance

Recognized by
OSHA, under 29 CFR 1910.7
Since
Rules in 1988; first lab recognized in 1989
On the list
21 organizations on October 12, 2026
Must be
Independent of the makers and sellers of what it certifies
Mark
Each lab uses its own registered certification mark

When a law says a plug-in solar system must be certified “by Underwriters Laboratories or an equivalent nationally recognized testing laboratory”, as California’s SB 868 does, it means a lab on OSHA’s list. OSHA’s FAQ defines an NRTL as a private-sector organization it has recognized as meeting the requirements in 29 CFR 1910.7, including complete independence from the manufacturers and vendors of the products it certifies.

Which labs are NRTLs?

OSHA keeps the current list. On October 12, 2026 it had 21 organizations, among them UL LLC, CSA Group, Intertek and TÜV Rheinland. Recognition covers specific standards, and OSHA says it doesn’t rank one lab’s experience against another’s.

How do I use this when I shop?

Each NRTL uses its own registered certification mark, according to OSHA’s program page. A mark on a box is a start; the proof is the lab’s own directory listing that exact model under the standard that matters, such as UL 3700 for a plug-in kit. Our guide on checking a UL 3700 listing shows how.

Published by the Plugged Sun editorial team

Sources

  1. Nationally Recognized Testing Laboratory (NRTL) Program (Official document, US Occupational Safety and Health Administration, 2026)
  2. Current List of NRTLs (Official document, US Occupational Safety and Health Administration, 2026)
  3. NRTL Program: Frequently Asked Questions (Official document, US Occupational Safety and Health Administration, 2026)
  4. UL Solutions Debuts Testing and Certification Framework for Safer Plug-In Solar Across the United States (Source, UL Solutions, 2026)

Where NRTL comes up