Hardware Reference
In-Depth Information
80 Plus
Whenitcomestocomputers,oneofthemajorfactorsinoverallenergyconsumptionisthe
efficiency of the power supply unit. In 2004, the Northwest Energy Efficiency Alliance
(NEEA) funded the 80 PLUS Program to encourage computer manufacturers to improve
the energy efficiency of their machines by installing highly efficient power supplies. Ecos
Consulting, who manages the program, tests and certifies power supplies as being 80%
(or higher) in efficiency. To help offset the cost of producing more efficient designs, the
program also pays incentives to manufacturers producing PSUs and systems that are cer-
tified.
Systems with more efficient power supplies consume on average from 15% to 30% less
power than conventional designs. This can result in a significant energy and cost savings
overthelifeofasystem.Inaddition,theresultinglowerheatoutputbothimprovessystem
reliability and saves additional energy in cooling the system as well as the surrounding
environment.
The 80 PLUS program currently has five levels of certification, from 80 PLUS to 80
PLUS Platinum. Each level of certification signifies different minimum levels of effi-
ciency, which are measured at three different loads (20%, 50%, and 100%).
Table 18.28
shows the details of each of the certification levels.
Table 18.28 80 PLUS Certification Levels
How is this efficiency determined, and what is the overall effect? The PSU in a PC con-
verts the high voltage (120V in the USA) AC wall current to 12V and lower DC voltages
for use in the PC. Unfortunately, no PSU is 100% efficient, meaning that some of the
power is lost or used up during the conversion and ends up being dissipated as heat. Con-
ventional PSUs are or were normally about 70% efficient, which means that 30% of the
energy drawn from the wall socket is wasted and ends up as heat. As an example, let's
take a system that draws 250 watts total.
Table 18.29
shows the resulting AC power draw
and the amount of wasted energy if the PSU were 70%, 80%, or 90% efficient.
Table 18.29 The Effect of PSU Efficiency on AC Power Draw and Wasted Energy
