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Report Compiled on New Energy Efficiency Standards for Gas Water Heaters
April 18, 2025
The Agency for Natural Resources and Energy (ANRE) has compiled a report on new energy efficiency standards for gas water heaters requiring manufacturers and other relevant parties to achieve about 3% improvement compared to fiscal 2022 levels in the energy consumption performance of these devices by fiscal 2028.
1. Overview
The working group on energy efficiency standards1 under ANRE has held meetings to discuss new energy efficiency standards for gas water heaters in accordance with the Top Runner Program under the Act on Rationalizing Energy Use and Shifting to Non-fossil Energy.2 As an outcome of the discussions, the working group has compiled the Report on the New Energy Efficiency Standards for gas water heaters.3
The report sets the target standard values to be achieved by fiscal 2028 (FY2028 standards) based on the anticipated maximum adoption rate of high-efficiency condensing water heaters. Ensuring the achievement of these target standard values and expanded use of condensing water heaters will require not only manufacturers but also the national government and businesses engaged in the distribution and promotion of water heaters to work together.
Water heating accounts for about 30% of energy consumption in the residential sector, making it the largest contributor to household energy consumption. In addition to the above-mentioned initiatives, ANRE will facilitate further energy conservation in the residential sector by promoting the introduction of high-efficiency water heaters, including Ene-Farm units, hybrid water heaters, and heat pump water heaters, and encouraging the broader adoption of condensing water heaters in rental apartment complexes.
2. Improvement rates of energy efficiency in the target fiscal year
The target standard values for gas water heaters are based on thermal efficiency (expressed as a percentage) as the performance indicator. The newly established standards require manufacturers to achieve an average thermal efficiency of 87.5%4 or higher for each fiscal year starting from 2028, the target fiscal year. Given that the average thermal efficiency of gas water heaters shipped in fiscal 2022 was 85%,5 this represents an efficiency improvement of about 3%.
The setting of this target standard value is based on the assumption that the adoption rate of condensing water heaters will exceed 57% (specifically 62% or higher in categories II through IV that include condensing water heaters) by fiscal 2028.
Table 1 Adoption rates of condensing water heaters
| Total | Category Ⅰ6 | Category Ⅱ | Category Ⅲ | Category Ⅳ | |
|---|---|---|---|---|---|
| FY2022 Actual | 37% | - | 6% | 54% | 72% |
| FY2028 Target | 57% | - | 35% | 75% | 83% |
3. Outline of the report
(1) Target gas water heaters
In line with the current standards, the new standards will apply to gas water heaters, excluding storage-type water heaters and those not covered by the Japanese Industrial Standards (JIS).
(2) Target fiscal year
FY2028
(3) Categories and target standard values
The next target standard values for gas water heaters are shown in the following table.
Table 2 Target standard values of gas water heaters
| Category | Target standard value | ||
|---|---|---|---|
| Name | Application | Ventilation method | |
| Ⅰ | Gas instant water heaters | Natural ventilation type | 77.6% |
| Ⅱ | Forced ventilation type | 85.6%×α II | |
| Ⅲ | Built-in gas bath heaters | 89.8%×α III | |
| Ⅳ | Gas water heater for space heating | 91.3% | |
Table 3 Structural coefficients αⅡ and αⅢ (categories II and III)
| Structure | Structural coefficient | |
|---|---|---|
| αⅡ | Through-the-wall type | 0.9981 |
| Wall built-in type | 0.9928 | |
| Forced flue type (with concentric pipe structure) | 0.9814 | |
| Forced exhaust type | 0.9802 | |
| Integrated with cooking range ventilator cover | 0.8307 | |
| Other | 1.0000 | |
| αⅢ | Through-the-wall type | 0.9921 |
| Wall built-in type | 0.9189 | |
| Other | 1.0000 |
(4) Assessment of target standard achievement and special provisions
Each category is required to meet its target value in each fiscal year from the target fiscal year onward.
Meanwhile, as a special provision to encourage manufacturers to actively increase the shipment share of products and categories with superior energy efficiency, target standard values not achieved in specific categories may still be deemed achieved if the manufacturer’s overall average energy efficiency exceeds the target standard value. In such cases, the calculation may include the energy efficiency and shipment volume of hybrid water heaters and residential fuel cells (Ene-Farm).
(5) Initiatives to promote wider adoption of condensing water heaters and similar systems
To ensure the achievement of the newly established target standard values and promote energy conservation in the residential sector, manufacturers are expected to implement initiatives to expand the use of condensing water heaters and similar systems in collaboration with the national government, as well as businesses and relevant parties involved in the distribution and promotion of water heaters. Meanwhile, the government will collect and publish drainage7 information from local governments, which is necessary when installing water heaters.
Notes:
- Working Group on Classification Standards for Gas and Petroleum Equipment of the Energy Efficiency and Conservation Subcommittee of the Committee on Energy Efficiency and Renewable Energy under the Advisory Committee for Natural Resources and Energy
- Act on Rationalizing Energy Use and Shifting to Non-fossil Energy
- Compiled by the Working Group on Classification Standards for Gas and Petroleum Equipment of the Energy Efficiency and Conservation Subcommittee of the Committee on Energy Efficiency and Renewable Energy under the Advisory Committee for Natural Resources and Energy.
- A weighted harmonic mean of the Top Runner values for conventional and condensing water heaters as of FY2022, calculated using the estimated market share of condensing water heaters in FY2028
- A weighted harmonic mean of the Top Runner values for conventional and condensing water heaters as of FY2022, calculated using the market share based on the shipment volume of each type in FY2022
- Category I does not include condensing water heaters.
- Condensate produced in condensing water heaters during the process of heating water using exhaust gas
Related Materials (in Japanese)
- Summary of the Compilation by the Working Group on Classification Standards for Gas and Petroleum Equipment (April 2025)(PDF:218KB)
- Compilation by the Working Group on Classification Standards for Gas and Petroleum Equipment of the Energy Efficiency and Conservation Subcommittee of the Committee on Energy Efficiency and Renewable Energy under the Advisory Committee for Natural Resources and Energy(PDF:3,800KB)
Division in Charge
Energy Efficiency Division, Energy Efficiency and Renewable Energy Department, Agency for Natural Resources and Energy
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