Recommendation from Climate Savers Computing Initiative ENERGY STAR Computer Server Draft 1 Tier 2 October 2009
ENERGY STAR for Computer Servers Tier 2 Draft 1 Recommendations (October 2009)
Introduction
The Climate Savers Computing Initiative (CSCI) is a nonprofit group of eco-conscious consumers,
businesses and conservation organizations working to cut the energy consumption of computers in half. As
participants in the Initiative, manufacturers commit to producing energy-efficient PCs, servers and
software, and members commit to using computer power management and purchasing energy-efficient
computers. The Initiative is also a resource for consumers and IT personnel who want to learn more about
reducing the power footprint of their computers—without any resulting loss of productivity.
Summary
ENERGY STAR's Tier 2 Version 1.0 Computer Server specification was the first draft in an iterative
process to develop the final ENERGY STAR Tier 2 Computer Server specification. Below Climate Savers
Computing Initiative (CSCI) has highlighted recommendations and justifications for changes to the Version
1.0 Tier 2 Computer Server specification.
Power Supply Requirements
ENERGY STAR proposal
Power supply efficiency testing and reporting provide useful metrics for users to evaluate power supply
performance and encourage improvements in power supply design. ENERGY STAR has indicated that
they will not pursue the Net Power Loss approach for measuring power supply performance. Rather the
Tier 2 Computer Server specification will continue "to address power supply requirements in terms of
efficiency and power factor....This combined approach supports industry's continued work to develop and
market more efficient power supplies for servers."
CSCI Recommendation
CSCI supports EPA’s conclusion that net power loss only be included in the Power and Performance
Datasheet. CSCI supports ENERGY STAR's decision to maintain power supply efficiency and power
factors as useful metrics for determining a power supply's energy efficiency. CSCI believes the proposed
efficiency requirement along with server idle requirements adequately ensure proper power supply sizing
for Energy Star enterprise servers. The Tier 2 power supply efficiency specifications for single and multi
O/P PSUs align with CSCI's planned specifications for gold level requirements for single O/P PSUs and
silver level requirements for multi O/P PSUs. In addition, the planned ENERGY STAR power factor
requirements align with CSCI's power factor requirements. CSCI also supports ENERGY STAR's decision
to eliminate the power factor requirement for PSUs operating below 75W as well as adopt the latest EPRI
PSU testing protocol. Finally, CSCI is collecting data to explore the impact of harmonic distortion when
increasing PF at light loads. CSCI hopes to have data for Draft 2 Tier 2 comments.
Table 2: Power Factor Requirements for Computer Server Power Supplies
Power Supply Type Rated Output Power 10%
Load
20%
Load
50%
Load
100%
Load
DC-DC (All) All Output Levels N/A N/A N/A N/A
AC-DC Multi-Output All Output Levels N/A 0.80 0.90 0.95
≤ 500 watts N/A 0.80 0.90 0.95
> 500 - 1,000 watts 0.65 0.80 0.90 0.95
AC-DC Single-Output
> 1,000 watts 0.80 0.90 0.90 0.95
CSCI proposes that the net power loss for a given test be estimated based on the input power to the server.
The server manufacturer can estimate the power lost in the power supply by using known efficiency curves
