Government plans revealed last week to make the energy consumption of public sector IT carbon neutral within four years contain a useful get out of jail free card ­ and one that will almost certainly be needed.

Any emissions that are not reduced will be offset, though it is made clear that this will be a “last resort” and will only happen through a scheme accredited by the Department of the Environment, Food and Rural Affairs (Defra).

As Cabinet Office minister Tom Watson, who launched the green IT strategy, said: “Turning off every one of Whitehall’s 500,000 computers at night would have the same effect as taking 40,000 cars off the road.”

This presents a dual problem. First, the only way to make 500,000 computers zero carbon without offsetting is to switch them all off permanently.

So some degree of offsetting will inevitably be involved, however much power use is reduced.

Second, the public sector is so huge that any kind of organisational change takes a long time to filter down.

Making machines turn to standby faster, activating screen savers, and putting printers on standby with dual-side printing are all measures that cannot be done centrally.

The Cabinet Office strategy identified this as a problem, saying: “The CIO Council will work with departments to ensure that staff embrace the challenge and are involved in the process wherever possible, identifying opportunities for awareness raising and sharing lessons learned.”

It is likely the Cabinet Office will encourage departments to use systems that can automatically power down PCs at night.

These strategies have been used by large organisations in the private sector, most notably HSBC ­ though none have claimed this is carbon neutral.

Departments will also be encouraged to look at thin client technologies, as well as virtualisation in the datacentre ­ this will be easier as it requires technical not cultural change.

These strategies have also been widely and successfully deployed in the private sector, most notably in the ever thrifty financial services sector. E.On Energy also managed to cut datacentre power costs by more than half.

Changing procurement practices may be easier, as they can be dictated by Whitehall purchasing body the Office of Government Commerce (OGC).

By January 2009, all procurement documentation must specify environmental criteria for IT in line with advice being developed by the OGC.

An investigation by Computing earlier this year found that green factors were not taken into account in Whitehall IT purchases.

But one government IT supplier said things are changing. “Cost and function are still the priorities, but green is moving up the agenda,” he said.