Applications Team and Energy Analysis Department

Investigate Standby Energy Use of New Internet Technology

Dale Sartor of the Applications Team (A-Team) recently switched his home computer to fast DSL access to the Internet. Noticing that the power supply and modem run hot to the touch, Dale contacted Alan Meier and Karen Rosen of the Energy Analysis Department. They outfitted him with a power monitor and sent him back home.

Sure enough, Dale found these devises can add 26% or 14 watts of “standby” load:

Table 1. Energy Use of PC in standby mode (watts)

	Power supply only[1]	Plugged in but “off”	Turned on but not being used
Westell WireSpeed DSL modem as supplied by Pacific Bell	1.4	1.4	7.4
Linksys DSL router with firewall	2.7	NA (no switch)	6.5
Hewlett Packard Desk Jet (ink jet) printer	2.4	2.4	7.7
Micron 17” monitor	NA	.7	2 (+/- 1) 2
Generic Pentium PC	NA	0	43 (+/- 3)
Total standby energy			67

[1] Equipment unplugged from power supply

2 Computer off or in Energy Star™ “sleep” mode

In the mode that many users leave their computer, the 67 watts of standby energy is about half the total energy when the computer and monitor is on, connected at high speed to the internet, and printing (138 watts on Dale’s PC).

The computer monitor remains the largest energy consumer for PC components. When Dale’s 17” monitor is on it consumes 52 to 61 watts (low when the screen is black and high with full colors). Many people use a screen saver. Screen savers don’t save energy. Therefore, standby energy use of a personal computer with a screen saver almost doubles. On Dale’s PC it increases to 122 watts. Fortunately Dale has an Energy Star ™ compliant monitor which powers down into a “sleep” mode after a set length of inactivity. His monitor goes to sleep after 15 minutes and the standby losses are reduced to 67 watts (with only 2 watts going to the monitor). Unfortunately, many computers that have this feature, don’t have it activated.

The DSL modem and router added 26% to Dale’s standby power consumption. In many cases turning the computer components off can eliminate standby power consumption. Karen Rosen reminds us that even that may leave the power supply and some internal equipment components “on” (11 watts in Dale’s case). Alan Meier’s recommendation – Turn off power at the power strip to eliminate all “leaking electricity” to power supplies and equipment.