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 and 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 es tablish and 
publicize standards  for manufacturers/importers  (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  gas or oil water heaters .  
The Minister also shall specify the matters to be labeled  by manufacturers, etc. with regard 
to energy efficiency of specified equipment including gas or oil water heaters.   
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 
and other related factors (as it is called the "Top Runner Program").  
The Minister propose s new energy efficiency standards for gas or oil water heaters to 
promote rationalization of energy use pertaining to gas or oil water heaters in Japan in order 
to cope with the recent increase of ene rgy consumption in the household  sector , climate 
change, and so forth.  
 
2. Outline of amendment  
(A) Scope  
(1) Gas water heaters ; gas instant water heaters, b ath tub water heater s and gas water heater s  
for space  heating 
(2) Oil water heaters ; appliances for hot water supply and for heaters   
 
 
(B) Energy consumption efficiency and measurement method 
(Gas water heaters)  
The energy consumption efficiency of appliances other than those with an air heating 
function is to be evaluated with the “mode thermal efficiency (%).” The m easurement 
method is set forth in the “ Measurement method of efficiency for domestic gas and oil 
water heater s under standard usage mode ” (JIS S 2075: 2011).  The energy consumption efficiency of appliances with an air heating function is to be 
evaluated by a weighted mean  of “rated thermal efficiency (%)” of the air heating part 
whose measurement method is set forth in the “Gas hydronic heating appliances for 
domestic use ” (JIS S 2112:2011) and the “ rated thermal efficiency (%)” of the hot  water 
supplying part whose measur ement method is set forth in the “Gas burning water heaters 
for domestic use ” (JIS S 2109:2019) in the ratio of 1:3 , as is in the current standards.  
 
(Oil water heaters ) 
The energy consumption efficiency of appliances other than those with an air heating 
function is to be evaluated with the “mode thermal efficiency (%).” Measurement method is 
set forth in the “Measurement method of efficiency for domestic gas and oil water heater s 
under standard usage mode ” (JIS S 2075: 2011).  
The energy consumption efficiency of appliances with  an air heating function is to be 
evaluated with the “ rated thermal efficiency (%)” as is in the current standards. As for the 
measurement method, it is evaluated based on the “ General rules for test methods of oil 
burning appl iances ” (JIS S 3031： 2009).  
 
(C) Target fiscal year  
The target fiscal year for both gas water heaters  and oil water heaters  is FY2025.  
 
(D) Category and targeted standard value  
(Gas water heaters ) 
The categor ies and targeted standard value s are as follows.  
 
Table 1. Targeted standard values  for gas water heaters  
Category  
Targeted 
standard value  Category  
name  Purpose  Ventilation type  
I 
Gas instant water heaters  Natural ventilation type  77.50%  
II Forced ventilation type  84.37%×αⅡ 
III Bath tub gas water heaters  87.21%×αⅢ 
IV Gas water heater s for space heating 90.32%  
 
Table 2. Structural coefficient s αⅡ, αⅢ (Category  II, III) 
 Structure  Structural 
coefficient value  
αⅡ Through -the-wall type 0.9998  
Wall built -in type  0.9869  Forced flue type  0.9900  
Forced exhaust type  
(limited to conventional type)  0.9661  
Integrated with cooking range ventilator cover  
(limited to conventional type)  0.8415  
Other 1.0000  
αⅢ Through -the-wall type 0.9839  
Wall built -in type  
(limited to conventional type)  0.9576  
Other 1.0000  
 
(Oil water heaters ) 
The categories and targeted standard values are as follows:  
 
Table 3. Targeted standard values for o il water heaters  
Category  
Targeted 
standard value  Category  
name  Purpose  Heating type 
I 
For hot 
water 
supply  Without 
bath use Instantaneous type  89.68% ×βⅠ 
II Storage type  76.88%  
III With bath 
use Instantaneous type  90.01% ×βⅢ 
IV Storage type  76.07%  
V 
For heaters  Storage type  
87.06% ×βⅤ 
 
Table 4 Structural coefficient s βⅠ, βⅢ, βⅤ (Category  I, III, V) 
 Structure  Structural 
coefficient value  
βⅠ Pressure -spray -type 0.9585  
Other 1.0000  
βⅢ Pressure -spray -type 0.9492  
Other 1.0000  
βⅤ On/off control  
(limited to conventional type)  1.0051  
Other 1.0000  
 
(E) Method to determine achievement  
The manufacturers of appliances  are required to keep the h armonic mean s of the energy consumption efficiency of appliances  shipped for each fiscal year starting from the targeted 
fiscal year,  weighted  with shipment volume  by category , at the same level or higher than the 
harmonic mean s of the standard  energy consumption efficiency weighted  with shipment 
volume  by category.  
 
(F) 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 FY2025.  
**As for labeling requirement, proposed date o f entry into force is around March of 2022.