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nit Energy Consumption by Machine Type Figure 5 shows unit energy consumptions (UECs) for the different equipment types. Typical baseline UECs for PC CPUs in 2005 are about 170 kWh/year, with Energy Star equipment reducing this by slightly less than 50%, to 90 kWh/year. Most of this reduction is attributable to savings in the Standby and Suspend modes, with only a slight reduction attributable to savings in Active mode power. Baseline PC CPUs show reductions in UECs relative to the 1990 stock of about 30%, from 240 kWh/year to 170 kWh/year, which is caused by reductions in microprocessor and peripheral power use for desktop machines. These improvements have been driven by the economics of chip manufacturing as well as by the manufacturer's desires to fit more peripherals into smaller spaces (an effort that requires heat reductions and hence efficiency improvements). Monitors show increasing UECs in the 2005 baseline relative to the 1990 stock. This increase is caused by the shift towards the almost universal use of color screens (and larger screens). Relative to the 2005 baseline, the Energy Star case shows a UEC reduction of about 30%, which is mainly the result of a reduction in Suspend mode power use. Active power use is not affected.

Laser printers show reductions in UECs of more than 50% in the Energy Star case relative to the 2005 baseline. These reductions are entirely the result of reductions in Suspend mode use. Active and Standby mode power use are not affected.

The UEC results for copiers are similar to those for printers in that only Suspend mode use is affected by the Energy Star program. Savings are about 30% relative to the 2005 baseline UEC.

Fax machines show about a 50% reduction in UEC relative to the 2005 baseline, with all of those savings coming from reductions in Standby mode power.

Minicomputer and mainframe UECs have been falling for years, as more and more of the functions previously handled by peripherals are integrated into fewer and fewer chips. Heat is an especially important issue in these machines (it reduces equipment lifetime), and the manufacturers have for this reason pushed to reduce energy use. We therefore expect 2005 baseline machines to show reductions in UECs of greater than 50% relative to the 1990 stock. UECs in Figure 5 only include direct power use of the computer equipment, and not any associated cooling energy required to keep the machines at their requisite temperatures. As smaller and smaller machines (especially parallel processing machines) take over the tasks previously assigned to large mainframes, the issue of secondary cooling will become less and less important for such computers.

The advanced scenario shows reductions in UECs relative to the Energy Star case of about 75% for PC CPUs and monitors, 20-40% for copiers and fax machines, and about 60% for laser printers and POS terminals. This scenario does not consider costs, so it is only an estimate of what is technically possible, not what is practically or cost-effectively achievable.  Last Updated On: 8/19/04