News and Events
Bunting Hall Energy Audit
April 2008
Audit Overview | Computers | Cooling/Heating | Lighting | Office Devices | Printers
Because desktop computers draw power when turned off, energy conservation results from setting them to sleep or hibernate during periods of inactivity throughout the day. In contrast, laptops can save more energy when unplugged overnight to avoid the standby loss from unnecessary charging.
Energy savings for desktop computers are based on a hibernation period of 30 minutes each day, a conservative estimate.
Computer Energy Savings
- 1 year: $40.08
- 5 years: $200.40
IBM ThinkCenter Towers (x9)
A common find in offices across campus, each IBM ThinkCenter Tower can be programmed to hibernate after 25 minutes.
Energy use: 73 watts
Action taken: 30 min inactive hibernation
Individual annual savings: $0.91
Combined annual savings: $8.19
(two in one office)
IBM Thinkvision/ThinkCenter Combo (x6)
An IBM Thinkvision monitor and corresponding IBM ThinkCenter tower can be set to hibernate when inactive.
Energy use: 114 watts
Action taken: 30 min inactive hibernation
Individual annual savings: $0.91
Combined annual savings: $5.46
Apple iMac 24" (x3)
Already efficient compared to traditional desktop computers, the Apple iMac 24" Core 2 Duo 2.4GHz can be set to hibernation for a greater reduction in energy use.
Energy use: 123 watts
Action taken: 30 min inactive hibernation
Individual annual savings: $1.53
Combined annual savings: $4.59
IBM Thinkvision/Lenovo Monitors (x14)
The IBM Thinkvision and Lenovo monitors draw the same amount of energy when in use.
Energy use: 41 watts
Action taken: 30 min inactive hibernation
Individual annual savings: $0.32
Combined annual savings: $4.48
Dual 2 GHz PowerPC G5 (x4)
The Dual 2 GHz PowerPC G5 can easily be set to hibernation automatically for greater efficiency.
Energy use: 119 watts
Action taken: 30 min inactive hibernation
Individual annual savings: $0.95
Combined annual savings: $3.80
Apple iMac G5
The Apple iMac G5 uses 138 watts when on, but only 3 when in hibernation.
Energy use: 138 watts
Action taken: 30 min inactive hibernation
Annual savings: $1.72
Combined annual savings: $3.44
PC/Mac Combo
The Pentium 4 3.40 GHz CPU uses 120 watts while the Dual 2 GHz PowerPC G5 draws 119.
Energy use: 239 watts
Action taken: 30 min inactive hibernation
Annual savings: $2.99
Apple Cinema Display (x3)
The 23" monitor uses 71 watts when active, and 1 watt when in hibernation.
Energy use: 71 watts
Action taken: 30 min inactive hibernation
Individual annual savings: $.89
Combined annual savings: $2.67
Laptops (x19)
Active laptop use ranges from 15-26 watts, and associated docking stations use about 32 watts. Even with a flat panel monitor (about 30 watts), the setup consumes less energy than a regular desktop computer. Because connected monitors and docking stations sleep when the laptop does, energy savings are gained by unplugging the laptop power adapter overnight.
With standby charging ranging from 1-3 watts, an average of 2 watts will be used to simplify calculations.
Energy use: 2 watts
Action taken: unplug overnight
Individual annual savings: $0.12
Combined annual savings: $2.28
The 20" Apple monitor (x4)
The 20" Apple monitor can be powered down in conjunction with its desktop unit.
Energy use: 28 watts
Action taken: 30 min inactive hibernation
Individual annual savings: $0.23
Combined annual savings: $0.92
PC/Mac Monitor Combo
While the 23" IBM Thinkvision monitor uses 30 fewer watts than the 23" Apple Cinema Display, the combined draw adds up quickly.
Energy use: 111 watts
Action taken: 30 min inactive hibernation
Annual savings: $0.88
Apple Cinema Display
The Apple Cinema flat-panel display averages 138 watts when on, with a steady drain when powered down.
Energy use: 3 watts
Action taken: unplug overnight
Individual annual savings: $.19
Combined annual savings: $0.38
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