What is PUE?

PUE is an obscure data center insider metric with huge economic and environmental implications. Ignore it at your peril.

An executive level introduction to PUE and why it matters

PUE (Power Usage Effectiveness) is a data center industry standard metric designed to allow data center operators to track efficiency improvements (or losses) over time.

It compares the ratio of total electrical power entering a data center and the amount of that power that ends up consumed by the IT equipment the data center was designed to house. For example, if servers require 10 KW of energy but the data center also needs + 5 KW to cool those servers down, the PUE would be 1.5.

What Drives PUE?

Whilst PUE is largely driven by cooling design, the climate conditions of where you locate your data center are also a large factor. Cool climates with predictable weather patterns offer significant advantages over hot and humid environments. For example. In Europe, PUE values of 2 are not unusual, particularly in legacy data centers. The EU average PUE is thought to be around 1.7. Some purpose-built single application data centers such as Facebook in Luleå, Sweden, achieve tremendously efficient PUE values in the region of 1.1.

Why Does PUE Matter?

Financial and environmental sustainability demand the most efficient use of resources. Paying 2x your electricity usage bill at home would be unacceptable to most people. And of course, the environmental penalty for gross inefficiency should be equally obvious. The planet is not proud of wasting 50% of server electricity on cooling, and that’s assuming your electricity was even green to start with.

PUE is a multiplier on your electricity costs

PUE and Colocation

If your colocation data center provider charges you PUE it means they are too inefficient to absorb it AND remain competitive. For example, if your service provider data center PUE is 1.5 it means adding 50% to your electricity bill. Even if you are in-house (on-premise) hosted, it’s on a colleague’s budget line, although perhaps they don’t know about it.

Hydro66 are unique in not charging a PUE overhead to colocation clients. Why can we do this? Simply put our 1.07 PUE means we can absorb a 7% inefficiency overhead. (Clue: start with the cheapest greenest electricity in the EU and build a massively efficient data center)

This is a significant factor in us being able to save our clients at least 50% on their colocation costs. And it becomes particularly important where, for example, an HPC (High Performance Computing) user needs a large amount of power. Today our standard Enterprise rack design is 10 KW and we are working hard on new designs to take this up much higher.

We encourage you to challenge your existing data center operator (in house, cloud or colocation) to be transparent about their PUE with you. Ask the question, look at your data center cost and strive to achieve better outcomes both environmentally and financially. The planet and future generations will thank you for your time.


Other businesses are saving 50% on hosting costs by moving their data to the Nordics. Don’t take our word for it – ask Gartner