Definition of energy efficiency for personal computers

Kaoru Kawamoto, Yoshiyuki Shimoda, and Minoru Mizuno, Osaka University

Keywords

personal computer, energy efficiency, definition, standards

Abstract

Though Japanese government adopted the mandatory program about the energy efficiency of personal computers, the definition of energy efficiency and its standards were not discussed enough. F or saving the energy use by energy efficiency standards , "energy efficiency" must reflect the amount of energy use per each unit . We conducted measurements of energy uses and performances for 5 desktop PCs and 5 portable PCs, and studied about the appropriate definition of energy efficiency and its standards for personal computers based on the measured results. We found that the ratio of power requirement to performance, which is the definition of energy efficiency for personal computers in Japanese mandatory program, is not appropriate for it, because more than 95% of energy use has no relationship with the computing loads. Instead, annual energy use, which is calculated from the average usage and the power requirement in each operating mode, is an appropriate definition of energy efficiency. The power requirement in idle mode, which decides more than 80% of annual energy use, can also be a simplified definition of energy efficiency. We also found that it is difficult to decide the standards of energy efficiency for personal computers, because there is almost no correlation between the performance and the energy use.

Paper

Download this paper as pdf: 4160Kawamoto.fm.pdf.

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