The Power Usage Effectiveness (PUE) metric is the most popular method of calculating energy efficiency in the data center. Although hotly debated for its limitations, its use is still very prevalent throughout the industry. Developed by the Green Grid, PUE is simply defined as the ratio of total facilities energy to IT equipment energy. It provides us a baseline to which we can measure against, but most importantly, it points us in the direction of where we’re not using our power effectively. This then allows us to make the changes needed so we can be using the power more efficiently. This is the main reason PUE is still so widely used in the industry. Simply put, you can’t manage what you don’t measure. If you’re trying to manage the efficiency of your data center, you have to measure PUE.

With that being said, there are three levels of measurement with PUE; levels 1, 2, and 3 (basic, intermediate, and advanced). At each level, the IT load is measured at different areas – the UPS outputs, PDU outputs, and directly from the IT equipment input, respectively. It’s also recommended that each PUE level is measured at different intervals – weekly, hourly, and 15 minutes or less, respectively. If you don’t feel overwhelmed at this point, we applaud you. If you do feel overwhelmed, hopefully the video below can help.