INTRODUCTION In recent years@ there has been a trend toward increased volumes of power consumed at data centers@ and this has become a problem from the perspective of reducing energy consumption. According to a survey report by the U.S. Environmental Protection Agency@ in data centers that house large numbers of IT equipment@ the volume of power consumed by the IT equipment is about the same as that consumed by devices on the facilities side@ including A/Cs@ lighting@ and power equipment. In order to reduce the power consumption at data centers@ it is therefore important to not only promote increased saving energy in IT equipment@ but also to increase the operating efficiency of facility side equipment@ and particularly A/Cs@ which consume large amounts of power. The authors focused on air cooled packaged air-conditioners@ which are used in many data centers in Japan@ and have been working on the development of constituent technologies that will contribute to saving energy in this equipment. We have succeeded in developing an A/C for data centers that incorporates these technologies. In this paper@ we will introduce these saving energy technologies and the operating efficiency characteristics of the newly developed A/C@ along with the results of field survey.