When shopping for a co-location provider or cloud supplier, evaluate PUE ratings to gauge long-term costs.
Power usage effectiveness is improving in U.S. data centers. More of the electricity brought into data centers is being used for compute purposes, and less for auxiliary purposes, such as cooling, security identification and lock systems, and lighting.
The efficiency gains are painful and accumulating slowly. At best, the average for all data centers, including enterprise data centers, is 1.9 or 1.8 instead of 2.0, as measured in the U.S. Department of Energy's 2007 data power consumption survey. The modest gains are described in an update to the DOE's original study released last year by The Energy Technologies Area of the Lawrence Berkeley National Lab.
PUE measures operational efficiency, calculated as the ratio of the average energy consumption of the entire data center to the average annual energy consumption by IT equipment alone. If your PUE ration is 1.0 – that is, all the power coming into the data center is used for compute purposes – you're perfect. But no one is. If nothing else, power is lost simply in the process of transport and distribution. The lower the PUE rating, the better.
Aligned Data Centers, a co-location service provider with data centers in Plano, Texas, and Phoenix, recently released a report that highlights the impact of PUE ratings on the amount a customer pays long term, whether that's for a co-location provider or cloud service supplier. The study, "Comparing PUE Between Colocation Data Centers – And Why It Matters," leverages data from the Lawrence Berkeley Lab report. Knowing what your provider's PUE rating is and understanding what it means to long-term costs is an essential element of effective workload outsourcing, Aligned said.
Customers are inevitably charged for their share of the total amount of electricity the facility uses in both co-location and cloud services.
Lowering PUE ratios is a stubborn problem for everyone. As large-scale modern data centers become denser with concentrated server racks and supporting equipment but require less personnel, power becomes a larger factor in overall costs. "Power typically represents 60-70% of the total operating cost of a data center," according to Aligned's report.
Aligned estimates that the cost of using a co-location facility with a PUE of 1.7 over 10 years is 48% more expensive than one with a PUE 1.15. (Aligned chose the 1.15 figure because its data centers have been earned that PUE ratio. It means only 15% of the power coming into their Plano, Texas facility is used for purposes other than compute.)
The difference in customer costs mount over a multi-year contract. For a 10-year period where the customer has one megawatt of equipment on site, with a kilowatt hour priced at $.06 at the start of the agreement, the 10-year bill comes to $6,929,227 at a 1.15 PUE facility. A data center with a PUE rating of 1.4 would end up with charges of $8,435,581. And at the less efficient 1.7 PUE facility, the bill would reach $10,243,205, according to the calculations in the report.
The figures refer to annualized PUE. A second type of PUE measure is design PUE, which measures the efficiency of use when the data center is operating at its peak load and is not represented in the figures. Annualized PUE is more closely related to IT operations.
After hyperscale data centers, co-location providers with their large-scale data centers had the next best PUE rating at 1.7 to 1.6 currently, according to Aligned. By 2020, that figure is expected to drop to 1.3.
Hyperscale data centers built by Facebook, Microsoft, Amazon, Apple and eBay, among others, are the ones most likely to operate at the lower end of the PUE ratings range as modern designs with minimized cooling costs. They typically operate with an annualized PUE of 1.2-1.13, according to Aligned's report, By 2020, that figure is expected to improve to 1.1, with just 10% of the electricity imported into a hyperscale data center going to keep lights on and equipment cool.
Enterprise data centers are widely regarded as operating at the upper end of the scale. They operate with PUEs of 1.9 to 1.79. By 2020, that figure may drop to 1.4, the report said.
The Green Grid, a nonprofit alliance of information and communications technologies companies that helped establish PUE ratings as a measure of efficiency, has some advice for enterprises trying to find out the PUE of a provider's facility. When inquiring about how data was collected for a PUE rating, prospective customers should find out the time frame over which it was collected and the type of data capture equipment that was used. Frequency of collection of key data points is another factor, according to the nonprofit.
PUE is one measure of how effectively a data center has been designed and constructed. If the PUE rating is low, the operator has a potential savings that can be shared with the customer. If the PUE rating is high, that reduces the supplier's options in offering the best rate to a customer over a multi-year period.