Electrical
28 Design Guide
3.5.8 Overall Power Supply Efficiency Levels
The efficiency of the power supply should be tested at nominal input voltage of 115
VAC input and 230 VAC input, under the load conditions defined in the Generalized
Test Protocol for Calculating the Energy Efficiency of Internal AC-DC and DC-
DC Power Supplies document. This document defines how to determine full load
criteria based on the label of each rail of the power supply. The loading condition for
testing efficiency represent fully loaded systems, typical (50%) loaded systems, and
light (20%) loaded systems.
The Efficiency requirements listed below are applicable to AC Input voltage of 115V.
Table 3-12: Efficiency Versus Load Minimum Requirements
Loading
Full Load
(100%)
Typical Load
(50%)
Light Load
(20%)
Required Minimum Efficiency 70% 72% 65%
Computers have decreased Idle power greatly since 2005, to where PSU loss is a big
concern for overall AC power of a computer in Idle Mode. The lowest DC load for
computers at this Idle Mode is determined to be 10 Watts for mainstream computers.
Computers with PSU larger than 500 Watts are also expected to have more
components and therefore the Idle Mode will be at a higher DC Load. The PSU above
500 Watts will use the Low Load Efficiency set at the 2% level. Low Load Efficiency
levels will be phased in over time. To help phase in these requirements a 12 Watt load
is defined for the first year. The three phases of increasing the Low Load Efficiency
requirements are shown in Table 3-13.
Table 3-13: Low Load Efficiency Requirements Increase Over Time
Required Date 12W/2% 10W/2%
September 2017 60% -
July 2018 - 60%
July 2020 - 70%
The 12 Watt and 10 Watt load conditions are defined in the Desktop Platform Form
Factors Power Supply Test Plan (# 595284).
3.5.9 Power Supply Efficiency for Energy Regulations - Energy
Star* and CEC PC Computers with High Expandability
Score - Recommended
The efficiency of the power supply should be tested at nominal input voltage of 115
VAC input and 230 VAC input, under the load conditions defined in the form factor
specific sections, and under the temperature and operating conditions defined in
Chapter 6
. The loading condition for testing efficiency represent fully loaded systems,
typical (50%) loaded systems, and light (20%) loaded systems. For system being sold
into the state of California that meet the High Expandability Computer definition
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