Managing Energy Costs in Data Centers

Data Centers

Data centers are notorious for their intensive energy consumption. According to the US Department of Commerce, these facilities can have power densities nearly 40 times higher than commercial office buildings, but those power densities vary significantly from one data center to the next. Because large, concentrated energy consumption is expensive and burdens the electrical grid, data centers are excellent targets for efficiency improvements. The first loads to evaluate in any load-reduction effort are the server and HVAC systems—the primary energy consumers in the data center (Figure 1)—and they can offer simple payback periods of a few years or less.

Average energy use data

Figure 1: Energy consumption by end use
In 2012, the US Energy Information Administration (EIA) conducted the Commercial Building Energy Consumption Survey (CBECS), which included energy end-use surveys for 800 buildings that contain data centers or server farms. The EIA estimates that these buildings represent nearly 97,000 facilities across the US, with only about 3% of buildings containing large data centers—more than 10,000 square feet; the vast majority of facilities are small or embedded data centers. It’s only in these largest facilities that we begin to see computing make up a larger fraction of total energy usage. Although CBECS data are weighted toward smaller facilities, they’re the best energy end-use data publicly available.
Pie chart showing electricity end uses in data centers. 20% cooling, 19% computing, 17% ventilation, 17% miscellaneous, 15% lighting, 6% refrigeration, 4% office equipment, 1% heating, 1% cooking
Pie chart showing natural gas end uses in data centers. 60% heating, 19% cooking, 17% water heating, 3% miscellaneous, 1% cooling
Top technology uses

Finding the best efficiency solution for a particular data center depends on its size, function, existing condition, and age. Some that work well for new construction aren’t good solutions for existing buildings, and data centers of different sizes often employ different energy-savings measures. For example, measures that work well in a server closet won’t perform sufficiently for hyperscale server farms. And solutions that work well for large data centers are often not feasible for smaller facilities due to cost or complexity. In order to choose the best energy solution, you need to understand where a data center facility lies along the spectrum of size and sophistication.

It’s best to target the IT power load with efficiency upgrades first because you can realize savings at little or no cost; later on, you can amplify those savings through the reduction of cooling loads. All of the power used by IT equipment eventually turns to heat, which the cooling system must then remove. Therefore, if the IT equipment uses less energy, the accompanying reduction in the facility’s cooling load will lead to additional energy savings. Although there’s considerable variation among facilities, a typical data center that reduces its computer load power requirements by 1.0 kilowatt (kW) would also offset approximately 0.6 kW of air-conditioning power (Figure 2).

Figure 2: Savings in IT energy use lead to significant upstream savings
Although the main purpose of a data center is to operate IT equipment, in this example, only 47% of the total power entering the data center directly powers the servers and chips. Within each server, an even smaller fraction of energy is actually used to provide valuable computing services.
Savings in IT energy use lead to significant upstream savings
Quick fixes
Longer-term solutions

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