The New Data Center Energy Efficiency Guidelines: the Five Ws and an H

In just over one year, it will be time to vote in the upcoming elections. Between the widely televised debates, heated exchanges and the mud-slinging, it feels more like the election is tomorrow! With so much time left, it would not be surprising if they ran out of topics to discuss. One thing that will likely not be discussed but that the new officials will need to consider once they take office is new energy efficiency guidelines for data centers. So, let’s use the “Five Ws and an H” method to break down the topic and make sure the voters are informed!


Why is there a need for change?

Though the standards that ASHRAE creates are not laws or codes by themselves, they are typically incorporated into the official building codes and then adopted by the state legislature. The current standard for energy efficiency in commercial buildings is ASHRAE 90.1. The requirements for data centers changed drastically when they were removed from the list of exempted facilities in the ASHRAE 90.1-2010. The standards were based heavily on prescriptive requirements for higher efficiency such as requiring economizers based on climate zones or triggering wholesale upgrades based on small additions, equipment replacements or retrofits. The 2013 update to 90.1 included allowances for performance based compliance, but relied heavily on PUE as the main measure of efficiency. The industry had major concerns about the possible effects on reliability, extreme capital costs and the restriction on creative designs and other innovative ways to save energy.


What is being done?

In response to the concerns, ASHRAE Standard 90.4P, Energy Standards for Data Center is being developed. The new standard will combine requirements on support spaces and systems such as lighting and envelope load from ASHRAE 90.1 with a new, more holistic approach based on overall mechanical and electrical performance and efficiency. It will also allow several paths to compliance as well as prescribing a way to consider system redundancy in the calculations.


Who does this apply to?

The standard begins by listing the major types of spaces that are excluded from the requirements. Telecommunication facilities are still excluded as well as a defined list of essential facilities including hospitals, national defense buildings, aviation control and others. In general, any other data center project that fits into the following categories is required to be in compliance.

  • New data centers – Total IT Equipment (ITE) Load greater than 10 kW and 20 W/ft2
  • Additions to existing data centers – Increase of greater than 10% in area or ITE Load
  • Alterations to existing data center – Includes replacement or upgrade of a building’s equipment or systems. Build out of a shell space or conversion of existing space is also included. Repair or direct replacement with the same technology is exempt.


How does this affect my data center projects?

The stated goal for the current performance requirements is that only the lowest performing systems, the bottom 20%, would not be in compliance. There are 3 paths to compliance for HVAC systems. Under the primary compliance paths, the Mechanical Load Component (MLC) is calculated by comparing the total power used by all of the equipment required to cool the IT equipment and supporting electrical infrastructure to the 100% ITE power. The MLC can either be based on the peak design conditions (kW) or the annualized calculations based on weather bin data (kWh) at 100% ITE Load. The alternate path is to calculate design PUE as previously prescribed in ASHRAE 90.1, Appendix G. Each of the Design MLC, Annualized MLC or PUE path have an associated table of values that must be met or exceeded depending on climate zone. The new standard also addresses electrical performance with the Electrical Loss Component (ELC) calculation. The ELC is calculated by determining the losses in the electrical distribution system dedicated to the IT equipment. The calculation encompasses everything after the medium voltage transformer through the branch circuit distribution. The minimum values and calculations are based on the system size and redundancy and calculated at 100% ITE load and 50% ITE load. There are several scenarios and trade-offs described in the standard.

CS Equation


When and Where is the change going to take place?

The second draft is currently out for review through October 19, 2015 with the goal to have the publication approved as an American National Standard (ANS) by the end of 2015. However, each state adopts new codes on their own schedule and most are one to two revisions behind the current edition of standard 90.1-2013, so there is still some time before this publication will be adopted in most states. For a full copy of ASHRAE 90.4P, Energy Standard for Data Centers, Second Public Review Draft, visit and click on the link for the draft copy of the standard. McKenney’s is here to help.


If you have questions regarding the new standards and how they affect your data center plans, leave your comment below, or reach out to us at



About Matt Rothwell


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Matt Rothwell manages the Critical Systems group at McKenney’s, which specializes in data center projects ranging in size and complexity with a focus on renovations, expansions, and greenfield projects. Matt, a graduate of Georgia Tech and former McKenney's co-op, works with his team to cultivate existing and new relationships through the development and implementation of energy savings strategies.

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