- 1 - Revisions of the M inisterial Ordinance and the Notification  
of the Ministry of Economy, Trade and Industry (METI)  
under the Act on the Rational Use of Energy  
 
Energy Efficiency Division 
Agency of Natural Resources and Energy 
Ministry of Economy, Trade an d Industry  
 
 
1. Background  
Under the Act on the Rational Use of Energy (Law No. 49 of 1979; hereinafter referred to as 
the “ Energy Efficiency Law ”), the Minister of Economy, Trade and Industry  shall establish and 
publicize standards for manufacturers/impor ters (hereinafter referred to as the  “manufacturers, 
etc.”) , with regard to the improvement of the energy efficiency performance for the respective 
equipment which is specified in Cabinet Order under the Energy Efficiency Law including 
magnetic disc units .  
The Minister also shall specify the matters to be labeled  by manufacturers, etc. with regard to 
energy efficiency of specified equipment including magnetic disc unit s.  
In addition , the energy efficiency standards shall be established taking into conside ration the 
highest level of energy consumption performance of the respective spec ified equipment and other 
related factors (as it is called the "Top Runner Program").  
The Minister propose s new energy efficiency standards for magnetic disc units to promote 
rationalization of energy use pertaining to magnetic disc units in Japan  in order to cope with the 
recent increase of ene rgy consumption in the business  sector, climate change, and so forth.  
 
2. Outline of amendment  
(1) Scope  
Magnetic disk unites  
Magnetic disk units  below  are exclude d. 
[i] Those whose use rate in markets is extremely small;  
i.e., Those whose storage capacity is one gigabyte or less.  
[ii] Those of which no measurement method has been  established and in which it is difficult to 
set any targe t standard;  
i.e., Those which work only based on power feeding through direct -current power sources, 
e.g., USB cables, not through alternative -current power sources.  
 
(2) Energy consumption efficiency and measurement method 
[i] Energy consumption efficiency  
Energy consumption efficiency should be a numer ical value representing measured electricity 
consumption by watt , which is divided by a value representing storage capacity by gigabyte.  
  
 
- 2 - [ii] Major measurement method of energy consumption efficiency 
In co nformity with international standards (ISO/IEC24091), energy consumption efficiency 
should be measured based on the following conditions.  
A. The ambient temperature should be from 18 to 28 degrees  Celsius, while the ambient humidity 
should be from 15 to 80%.  
B. The range of power source voltage should be ±1% of the voltage if the rated electricity 
consumption is 1,500W or less, while it should be ±5% if the rated electricity consumption is 
over 1,500W.  
C. The frequency of the power source should be a rated frequency.  
D. Magnetic disk units  on which 12 or more disk drives can be mounted should be measured 
when they comprise a necessary power source, a ca che memory for buffer and a control device 
and they have a structure in which a storage capacity connectabl e to the control device  reach es 
the maximum (hereinafter referred to as “maximum structure”). Manufacturers are permitted to 
calculate energy consumption efficiency by making use of calculation formulae if they face 
difficulties in conducting an actual measurement of  the efficiency by making use of the 
maximum structure.  
 
(electricity consumption  of the basic housing ) + (electricity consumption  of the expansion  
housing) × (the number of expansion housings)  
 
(3) Target fiscal year  
The target fiscal year is F Y2023.  
 
(4) Categories and target standard values  
Categories and target standard values of magnetic disk units  are stipulated as below.  
 
Target standard values of magnetic disk units  
Number of 
mountable 
disk drives  Style and performance of disk drives  
 Category 
names  
 Standard energy consumption 
calculation formulae  
External 
dimensions of disk 
drives  Number of 
disks  
1 - 1 I E＝exp(2.98×ln(N) -30.8)  
2 or 3 II E＝exp(2.98×ln(N) -31.2)  
4 or more  III E＝exp(2.11×ln(N) -23.5)  
2 to 11  - - IV E＝exp(1.56×ln(N) -17.7)  
12 or more  Having structures 
containing 3.5- inch 
disk drives  - V 0.00170  
Having structures 
consisting of 2.5- inch - VI E＝exp(0.952×ln(N) -14.2)   
 
- 3 - disk drives alone  
Note 1: The letters “E” and “N” in the respective target standard values refer to the numerical 
values represen ted by the following items.  
E: Energy efficiency  standards (unit: watt/gigabyte)  
N: Number of re volutions  (unit: rate per minute)  
Note 2: The term “In” refers to logarithm having “e” as the base.  
Note 3: When multiple disk drives with different revolution  rates are mounted in one device, 
the revolution  rate (N) should be the weighted average of the revolution  rates of the 
respective disk drives based on the number of installed drives.  
 
(5) Method to determine achievement  
Concerning magnetic disk devices shipped to domestic markets in each fiscal year following the 
target fiscal year, the respective ma nufacturers and other businesses should ensure  that the 
weighted average based on the number of shipped magnetic disk units  per category (as for a unit 
having multiple disk drives, the number of basic housing s) should not exceed the weighted 
average of the  energy efficiency  standards  based on the number of shipped magnetic disk units . 
 
(6) Labeling requirement   
These revisions include requirements that manufacturers , etc.  should indicate on their catalog s 
with regard to energy consumption efficiency etc.  
 
4. Proposed date of entry into force  
Around April of 2021* (except labeling requirement**).  
*Target fiscal year for achieving the new standard is set to be FY2023 . 
**As for labeling requirement, proposed date of entry into force is around March of 2022.