A new £5.2 million Scottish Government datacentre, completed last year, will use two-and-a-half times as much electrical power per year as a facility built to the best modern standards.

A freedom of information request has uncovered that the 15,000sqft Saughton House facility in Edinburgh, one of 120 used by the Scottish public sector, has a "power usage effectiveness" (PUE) rating of 2.7, equating to a 37% efficiency rating. Calculations based on the 10p per-kilowatt-hour cost of electricity to the one megawatt datacentre reveal the facility will cost the taxpayer up to £7.14m in extra energy costs over five years, emitting an extra 38,000 tonnes of CO2 emissions, compared to a datacentre of the same size built to more up-to-date designs.

PUE is the cost of mechanical and electrical power required to create optimum atmospheric conditions for massed servers, over and above the cost of powering the servers themselves. While a PUE of one (equal to 100% efficiency) is unachievable, some private datacentres – including an Edinburgh centre by Onyx unveiled last week – have already reached a PUE of 1.2 (83% efficiency). The most up-to-date facilities, including those in the Republic of Ireland, have achieved PUE as low as 1.07 (93%).

Derek Schwartz, director of the Green Data Center Alliance (GDCA), a not-for-profit body that campaigns for better energy efficiency in data processing, said a 2.7 PUE rating for a new datacentre was "outrageous in this day and age" and urged the Scottish Government to consider predicted rises in the cost of energy when planning future data provision.

A spokesman for the Scottish Government, which has described Scotland's datacentres as "world-class", said: "The current PUE of the Scottish Government datacentre has been calculated at a figure of 2.7. As measures to optimise energy efficiency are fully implemented, we expect the PUE to improve to a figure closer to 1.4."

However, industry experts have questioned whether the lower figure is achievable in a "legacy" 1980s facility like the refurbished Saughton House. Even if the lower 1.4 PUE were achieved quickly, the facility would still consume £1.45m more in electricity than a state-of-the-art datacentre within five years, emitting an extra 7583 tonnes of CO2.

Lower PUEs have been achieved through use of "free air cooling", allowing outside air to circulate freely around the servers as recommended by the 2009 EU code of conduct. According to the Scottish Government, Saughton House is only 54% occupied and will not be at full capacity until 2015.

Schwartz said: "In this day and age a PUE of 2.7 is outrageous, and I bet you they won't be at 1.4 either even if the centre is fully populated, as it is very hard to achieve in a facility where efficiency is not built in at the start."

Edinburgh Green Councillor Gavin Corbett told the Sunday Herald: "I'm deeply disturbed to hear that we in Scotland are achieving such a poor standard of energy efficiency in our datacentres, and I will be asking my MSP colleagues to raise this with ministers.

"Scotland is rightly proud of having some of the world's best targets to increase energy efficiency and reduce emissions but that clearly only works if we take the practical measures that allow us to achieve that."

The Scottish Government spokesman declined to respond to questions on whether energy efficiency was a condition in the tendering process for the new facility. Asked whether PUE would be a consideration in procurement of future datacentres, he said: "This will be considered as part of the overall consolidation strategy for the public sector to ensure both transition and development is cost-effective."