Basic Information about UL Standards

Underwriters Laboratories (since 2022 renamed to UL Solutions) created the UL standards as product safety requirements for the American market starting more than one century ago. After completing the test, products that meet these requirements can be given a label that clearly states their UL certification. For the sales of a huge variety of goods in the USA, the UL certification is essential.
UL solutions is an independent US organization that can be compared to the German TÜV.

Why is the UL marking or seal important?

Over the past century, Underwriters Laboratories has become the world's best-known independent product safety certification organization. Every year, millions of products and their components are tested according to strict UL safety standards. Therefore, the UL seal has a high priority, especially on the US market, as the product liability laws here are even stricter than in Europe. It ensures that products meet their set safety and quality standards.

CLOU Energy Storage Container (Symbol Image CLOU AI)
CLOU Energy Storage Container (Symbol Image CLOU AI)
Various colours optional

Differences in certification

There is no general UL approval. Rather, it is divided into different stages:

  • UL Recognized
    The UL Recognized seal of approval is often issued for components that are used in a product with the UL Listed seal. These are, for example, printed circuit boards or power supplies.
  • UL Listed
    In comparison to the UL Recognized seal of approval, the UL Listed seal is awarded for entire products. For the award of the seal, the product is subjected to far more tests than are necessary for the UL Recognized seal.
    The UL Listed seal means that the product has been tested by UL to nationally recognized safety and sustainability standards. A UL-listed approval thus ensures the safety and longevity of many household items under normal wear and tear in daily use and is therefore considered a quality feature, especially by US customers.
  • UL Classified
    UL classified products are tested only for specific properties, a limited range of hazards, or suitability for use under restricted conditions. If a product is UL classified, it meets the requirements of one, but not all, of the tests that are normally part of a standard.

However, for obtaining a seal, there is not one test that is applied to all products to be tested. Rather, a test is always adapted to the product type. For this, there are different categories and classes, according to whose safety regulations the product is tested.
In order to be allowed to use the UL seal in the long term, manufacturers must ensure that their certified products permanently meet the relevant safety requirements.

What is the difference between CE- and UL-certificates?

Unlike the European CE marking, the UL mark is not mandated by law.
The manufacturer agrees to follow the CE regulations by using the CE mark.
In comparison, devices that will bear the UL mark must be independently certified by UL.
A product bearing the CE symbol may also bear the UL or other seal of approval.


UL Solutions is an independent US organization that certifies products for the US market, similar to the German TÜV. For CLOU the UL certification is in place for electrical energy storage (ESS), while our energy meters for the North American market are holding ANSI (American National Standards Institute) certificates.

If you have questions or specific certification requirements, please contact us.

Editor's note: This article was originally published in March 2023 and has been updated for comprehensiveness.

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