Revisions of the Notification of the Ministry of Economy, Trade and Industry (METI)  
under the Act on Rationalizing Energy Use and Shifting to Non -fossil Energy  
June  2023  
Energy Efficiency Division  
Agency of Natural Resources and Energy  
Ministry of Economy, Trade and Industry  
 
1. Ba ckground  
Under  Article 149 of  the Act on Rationalizing Energy Use and Shifting to Non -fossil 
Energy  (Act No. 49 of 197 9; hereinafter referred to as the “Energy Efficiency  Act”), the 
Minister of Economy, Trade and Industry  shall es tablish and publicize the energy efficiency 
standards  for manufacturers/importers  (hereinafter referred to as the “manufacturers, etc.”) , 
with regard to the improvement of the energy efficiency performance for the respec tive 
specified equipment  which is stipulated in the Enforcement  Ordinance  under the Energy 
Efficiency Act including  transformers  (For building and factory)  .  
In addition , the energy efficiency standards shall be established taking into consideration 
the highest level of energy consumption performance of the respective spec ified equipment , 
future prospect s for technological development , and other related factors.  
 In order t o promote rationalization of energy use pertaining to  transformer s (For 
building and factory)  in Japan and cope with the recent increase of ene rgy consumption in 
the commercial sector , climate change, and so forth , new energy efficiency standards for 
transformers  (For building and factory)  are to be established and publicized . 
 
2. Outline of Revisions  
(A) Scope  
Transformers  (For building and factory)   
 
(B) Energy consumption efficiency and measurement method  
Energy consumption efficiency shall be the total loss acquired through the no -load loss and 
load loss measured using the method stipulated by JIS C 4304 and JIS C 4306 . The energy 
consumption efficiency shall be calculated by the following formula.  
 
E=Wi+(m
100)2
×Wc 
 
In this equation, E, Wi, m, and Wc individually represent the following numerical values.  
E: The total loss  (W)  m: Standard load factor (40 for those with a rated capacity of 500 kV A or less, and 50 for 
those with a rated capacity of over 500 kV A.) (%) 
Wi: The no -load loss  (W) 
Wc: The load loss  (W) 
 
(C) Target fiscal year  
   FY2026.  
 
(D) Category and Targeted Standard Value 
The categories and targeted standard value s are as follows.  
 
Table. Categor ies and Targeted Standard Value s of Transformers  
Category  Standard energy 
consumption calculation 
formula  Category 
name  Transformer 
type Number of 
phases  Rated 
frequency  Rated 
capacity  Specification  
3-1 Oil-filled 
transformer  
 Single phase  50Hz  Up to 500kVA  Standard 
specification  
 Ｅ= 9.34・(kVA)0.737 
3-2 60Hz  Up to 500kVA  Ｅ= 8.60・(kVA)0.744 
3-3 Triple phase  50Hz  Up to 500kVA  Ｅ= 14.5・(kVA)0.694 
3-4 Over 500kVA  Ｅ= 10.6・(kVA)0.797 
3-5 60Hz  Up to 500kVA  Ｅ= 14.4・(kVA)0.681 
3-6 Over 500kVA  Ｅ= 8.00・(kVA)0.825 
3-7 Molded 
transformer  
 Single phase  50Hz  Up to 500kVA  Ｅ= 14.1・(kVA)0.685 
3-8 60Hz  Up to 500kVA  Ｅ= 13.3・(kVA)0.692 
3-9 Triple phase  50Hz  Up to 500kVA  Ｅ= 16.9・(kVA)0.699 
3-10 Over 500kVA  Ｅ= 31.2・(kVA)0.659 
3-11 60Hz  Up to 500kVA  Ｅ= 16.2・(kVA)0.702 
3-12 Over 500kVA  Ｅ= 17.4・(kVA)0.742 
3-13 Oil-filled 
transformer  Single phase  50Hz  Up to 500kVA  Semi -
standard 
specification  
 Ｅ=(9.34・(kVA)0.737)・1.10 
3-14 60Hz  Up to 500kVA  Ｅ=（8.60・(kVA)0.744）・1.10 
3-15 Triple phase  50Hz  Up to 500kVA  Ｅ=（14.5・(kVA)0.694）・1.10 
3-16 Over 500kVA  Ｅ=（10.6・(kVA)0.797）・1.10 
3-17 60Hz  Up to 500kVA  Ｅ=（14.4・(kVA)0.681）・1.10 
3-18 Over 500kVA  Ｅ=（8.00・(kVA)0.825）・1.10 
3-19 Molded 
transformer  
 Single phase  50Hz  Up to 500kVA  Ｅ=（14.1・(kVA)0.685）・1.05 
3-20 60Hz  Up to 500kVA  Ｅ=（13.3・(kVA)0.692）・1.05 
3-21 Triple phase  50Hz  Up to 500kVA  Ｅ=（16.9・(kVA)0.699）・1.05 
3-22 Over 500kVA  Ｅ=（31.2・(kVA)0.659）・1.05 3-23 60Hz  Up to 500kVA  Ｅ=（16.2・(kVA)0.702）・1.05 
3-24 Over 500kVA  Ｅ=（17.4・(kVA)0.742）・1.05 
E: Standard energy consumption efficiency （unit: W） 
 
(E) Method of determin ing achievement  
The value of e nergy consumption efficiency of the equipment shipped in each fiscal year 
after the target year, which is the weighted average  based on  the number of units shipped for 
each category, should not exceed the value of the energy efficiency standard, which is the 
weighted average  based on  the number of units shipped for each category.  
 
(F) Labeling requirement  
These revisions include requiremen ts that manufacturers, etc. shall indicate in their 
catalogs with regard to energy consumption efficiency etc.  
 
3. Proposed date of entry into force  
Around  September  2023*  
*Target fiscal year for achieving the new standard is set to be FY 2026 .