Since installing IBM blade servers and Eaton uninterruptible power supply (UPS) blades in its data centre the organisation has been conducting power audits once or twice a year, but now plans to monitor power consumption real time.

Jones said that the two big power consumers in the data centre are the UPS units and air-conditioning. Energy audits have shown the virtualised data centre saves 140,000 tonnes of CO2 and $23,000 a year. For Corporate Express, which voluntarily reports its carbon footprint as part of the Carbon Disclosure Project, having a good handle on its emissions is important.

But as Jones explained: “One of the things with an audit is it is just a snapshot in time - we had planned to do that biannually, but now we think there will be more benefit from a more real time PUE (power usage effectiveness) measurement.”

The PUE, a power usage metric developed by the industry consortium Green Grid, is defined as the total facility power (power going into the data centre) divided by the IT equipment power, so a PUE of 3 would mean it takes three times as much energy to power the data centre as to power the IT equipment where a PUE of 1 suggests complete efficiency where all the power to the data centre is being used to power IT (rather than power the lights, air conditioners or lost through power leakage).

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