Output Curtailment of Renewable Energy Expected to Rise to 3% in Tohoku Region

Output Curtailment of Renewable Energy Expected to Rise to 3% in Tohoku Region
Increase Observed in Hokkaido, Tohoku, Shikoku, and Kyushu
September 25, 2025

Key Observations

1. Seasonal Pattern

   • Curtailment is highly concentrated in spring (March–May) each year.

   • This is because electricity demand is relatively low in spring, while solar generation peaks, creating excess supply that must be curtailed.

2. Growth Trend

   • FY2021: Curtailment was relatively small (< 2 billion kWh per month).

   • FY2022: Noticeable increase, especially in April–May (Kyushu and Tohoku contributed most).

   • FY2023: Another rise, reaching nearly 5 billion kWh curtailed in May.

   • FY2024: Continues at a high level, with similar seasonal peaks.

   • FY2025 forecast: The highest ever → exceeding 7–8 billion kWh in April–May nationwide.

3. Regional Contribution (color-coded)

   • Kyushu (dark blue) remains the largest contributor to curtailment each year.

   • Tohoku (red) and Chugoku / Shikoku (green/gray) are increasingly significant.

   • Hokkaido (light blue) and Hokuriku (light green) show moderate curtailment.

   • Tokyo (purple) and Okinawa (light gray) barely contribute.

4. Implications

   • Curtailment volumes are projected to almost double from 2021 to 2025, reflecting grid constraints.

   • Reinforces the need for:

     • Grid expansion / interconnections (e.g., Kyushu–Honshu tie line)

     • Battery energy storage systems (BESS)

     • Flexible demand management (demand response, EV charging optimization)

At the 4th meeting of the “Next-Generation Power System Working Group” held by Japan’s Ministry of Economy, Trade and Industry (METI) on September 24, officials reported that the rapid expansion of renewable energy has led to a broader application of output curtailment across the country. Output control volumes are increasing, driven by both reduced interregional power transfers and lower electricity demand due to simultaneous curtailment in multiple regions.

Annual Output Curtailment of Renewable Energy by Region (Japan)

1. Annual Curtailment Rates (Top = curtailed electricity [kWh], Bottom = annual demand [kWh])

• Kyushu (九州)

  • 2018: 0.9% (864 GWh)

  • 2019: 4.0% (844 GWh)

  • 2020–2023: fluctuating 2.9–3.0%

  • 2024: 4.0% (880 GWh)

  • 2025 forecast: 6.1% → the highest in Japan

• Hokkaido (北海道)

  • 2022: 0.04% (191 GWh)

  • 2023: 0.01%

  • 2024: 0.04% (269 GWh)

  • 2025 forecast: 0.3%

• Tohoku (東北)

  • 2022: 0.5% (6,379 GWh)

  • 2023: 1.6%

  • 2024: 2.3% (7,920 GWh)

  • 2025 forecast: 2.2%

• Chubu (中部)

  • 2022: 0.2%

  • 2023: 0.2%

  • 2024: 0.5% (3,782 GWh)

  • 2025 forecast: 0.4%

• Hokuriku (北陸)

  • 2022: 0.9%

  • 2023: 1.6%

  • 2024: 2.1% (1,652 GWh)

  • 2025 forecast: 2.1%

• Kansai (関西)

  • 2022: 0.1%

  • 2023: 0.2%

  • 2024: 2.1% (1,348 GWh)

• Chugoku (中国)

  • 2022: 0.5%

  • 2023: 3.6%

  • 2024: 2.3% (5,100 GWh)

  • 2025 forecast: 2.8%

• Shikoku (四国)

  • 2022: 1.0%

  • 2023: 1.8%

  • 2024: 1.9% (9,229 GWh)

  • 2025 forecast: 2.4%

• Okinawa (沖縄)

  • 2022: 0.03%

  • 2023: 0.08%

  • 2024: 0.15% (705 GWh)

  • 2025 forecast: 0.2%

• Tokyo area (東京)

  • Extremely low curtailment: 0.009% forecast for 2025

2. Installed Renewable Capacity (March 2025)

FY2024 Curtailment Levels by Region

• Kyushu: 4.8% (750 million kWh) – the highest curtailment rate nationwide

• Hokkaido: 0.04% (2.69 million kWh)

• Tohoku: 1.3% (210 million kWh)

• Chubu: 0.3% (50.99 million kWh)

• Hokuriku: 0.9% (16.52 million kWh)

• Kansai: 2.1% (200 million kWh)

• Chugoku: 2.3% (210 million kWh)

• Shikoku: 3.2% (160 million kWh)

• Okinawa: 0.15% (0.7 million kWh)

Updated FY2025 Forecasts

Compared to the initial forecast reported in January 2025, curtailment rates have been revised upward in:

• Hokkaido: 0.3% (from 0.04%)

• Tohoku: 3.0% (from 2.2%)

• Tokyo: 0.042% (from 0.009%)

• Kansai: 0.6% (from 0.4%)

• Shikoku: 3.8% (from 2.4%)

And revised downward in:

• Chubu: 0.3% (from 0.4%)

• Chugoku: 1.5% (from 2.8%)

• Kyushu: 5.9% (from 6.1%)

• Okinawa: 0.09% (from 0.2%)

3. Key Takeaways

• Kyushu is the most heavily affected region due to very high solar penetration → forecast curtailment 6.1% in 2025.

• Hokkaido, Tohoku, Shikoku, Chugoku are also seeing rising curtailment (2–3%).

• Tokyo region essentially faces no curtailment thanks to stronger grid connections and high demand.

• The data suggests that grid balancing, storage solutions (BESS), and inter-regional transmission upgrades are crucial to reduce renewable curtailment in the coming years.

Contributing Factors

• Drivers of increase: higher renewable energy penetration, higher hydro output from heavy rainfall, weather fluctuations (e.g., stronger solar radiation), lower demand in some regions, and outages or maintenance of pumped-storage hydro plants.

• Drivers of decrease: higher demand in some regions, outages or maintenance at thermal plants, and increased use of interconnection lines.

Overall, Hokkaido, Tohoku, Shikoku, and Kyushu are projected to see higher curtailment levels in FY2025, with Tohoku’s rate reaching 3%, reflecting growing integration challenges as renewable capacity expands.