Saving money using power management has been a well worn mantra in the data centre for some time, but now Gartner has put a cash figure on the likely cost savings from managing an organisation's PC power consumption - $43,300 (£29,300) per year.

The analyst company said that the total power consumption (per year) for a "well-managed 2,500-PC organisation is 43 percent lower than an unmanaged one." This, Gartner has calculated, means that organisations actively employing power management functionality can expect to save $43,300 (£29,335) per year, compared with an unmanaged 2,500-PC organisation.

Another $6,500 (£4,400) can be saved per annum by turning off and unplugging machines from the electrical socket (even when switched off, PCs consume some power when left plugged in). However Gartner warns this could affect staff productivity because updates will need to be carried out during working hours, and it is somewhat impractical to do this in reality.

"Much attention on power consumption has focused on the data centre, but PC power consumption in an organisation can also be significant, especially given steadily rising electricity prices," said Federica Troni, principal analyst at Gartner.

"IT organisations should recognise that the greatest savings come from employing power management features. They should investigate the power management capabilities of their PC life cycle management tools and PC power management point solutions to implement these policies and to better support management activities."

Gartner has even created a model - actually an Excel spreadsheet - to assess the impact of different variables on an organisation's total PC power use, although this model is only available to Gartner's customer base and not the general public. The model makes use of a number of common assumptions in order to make these calculations.

These assumptions include that there are 2,500 staff in the organisation; the ratio of PCs to employees is 1-to-1; staff work an eight-hour business day 230 days per year; and active use of the PC during working hours is 70 percent of the time. The power calculation assumes a cost of $0.1 (6 pence) for one kilowatt-hour (kWh).

Using these parameters, Gartner's model can calculate the power consumption for desktops, notebooks and associated monitors during the workday and after hours. The model is based on three different scenarios - the well-managed, unmanaged and unplugged organisation.

"There are many calculators around these days, including the Energy Star one, as well as vendor specific ones, which are a little less credible," Troni told Techworld. "Ours differs from other ratings, because it can work how much power you consume, how much CO2 you consume, and how you would cost any emission change if you changed any rules or policies around power management."

She said the spreadsheet allowed for a customer to input their number of laptop, desktops, as well as other information needed, such as how many CRT or LCD monitors are used, whether PCs are switched off at night, or left in standby mode, or left powered on, etc.

"Once all the data is entered, the model tell you how much power your PCs are using, and how much is company power. We also inputted some conversion rates to understand the carbon emission you generate," she said. "You can put in an average figure for power price. You can customise the characteristics of your equipment, for example if the specifications for two year old PCs, etc."

The annual cost savings associated with a well-managed environment versus an unmanaged one is $43,300. This assumes that all power is paid for by the organisation. Excluding the power consumed when mobile PCs are used off the organisation's premises, the annual cost saving is calculated to be $27,500 (£18,631).

"Projects on power management are successful, because they save money and it is green," said Troni. "It also doesn't cost a great deal of money to do, as companies can look at relatively cheap third-party power management applications such as those like 1E's NightWatchman."

"These are fairly inexpensive products that can reduce power consumption while allowing for updates, and absolutely companies should be looking at products like this," Troni said. However, she warned that companies must be reasonable when designing their power management plans. "For example, when you put a user's PC into standby mode, this standby mode must not happen too quickly or it irritates the user and it will be abandoned."