UL Numbers From Underwriters Laboratories
"Underwriters Laboratories, an independent firm working with product safety certification, has been active in the field of product testing and preparation of safety standards for more than a century. UL evaluates more than 19 000 types of products, components, materials and systems annually. Every year more than 20 billion UL marks are placed on products from 66 000 different manufacturers. The UL Group and its network of service providers include 68 testing and certification labs worldwide, serving customers in 102 countries."--From the About UL page at ul.com
Essentially, this means that all PSUs sold on the North American market must be marked with a UL number. This number should identify the actual manufacturer of a product. However, not every PSU has such a number. UL number omission on a North American product might indicate poor quality.
Step 1: Reading the UL Number
To find the UL number, there's no need to open your PSU or de-solder anything. Simply open your PC and look at the power supply's label. The UL number usually begins with an "E" followed by a string of numbers. See the three examples below.



If your PSU has such a number, you can move onto the next step, finding out what it means.
Online UL Number Query

Now let's find out more about your PSU. Go to the UL Online Certifications Directory and enter the UL number in the UL File Number field. If the number exists in the database, you should immediately see the result. If not, the number is invalid, fake, or the manufacturer no longer exists.
Link: Online Certifications Directory
We want to stress two things in particular:
A PSU is not necessarily bad because it is cheap. But the lower the price, the more you'll likely have to skimp on safety and performance features. A high-quality PSU contains more expensive components. If you buy cheap, you might have to buy twice--or more.
A PSU is not automatically inferior because it was made by a contractor with which you aren't familiar. These companies make all kinds of products, from luxury brands to pure garbage. Again, it's a question of hitting different production targets. Is the product built for quality or aggressive cost reduction? The responsibility always lies with the buyer to recognize and reject products that are obviously unsuitable.
Some quality issues, such as those seen with Be Quiet's P6 series, present an additional aspect to consider, while we can also see that companies like Super Flower are often underestimated because they are not as seen and accepted as the large manufacturer, which in fact they are.
We thank our readers again for their help. We will continue to collect new results and regularly update the lists. They are, after all, a rough guide to what goes on behind the scenes in the power supply industry.
Just one question - which OEMs are most likely to put out quality hardware? You mention that Topower, Andyson, Enhance, Channel Well etc aren't good options, so which OEMs should we look for?
And even more disappointing is the fact some of those non-Enermax ones have a hefty, Enermax-like, price tag.