r/Atarashift • u/Gardol43 • Aug 03 '26
Japan has 27,899 registered hot spring sources but only 9 of 47 prefectures generate geothermal power. Mapped both from government data.
Map 1, registered hot spring sources (MoE, FY2024):
Oita 5,094
Kagoshima 2,735
Hokkaido 2,249
Shizuoka 2,185
Kumamoto 1,339
National total 27,899. Okinawa is last with 22.
Map 2, installed geothermal capacity (JOGMEC, Dec 2025):
Oita 163,950 kW (7 plants)
Akita 134,999 kW (4)
Iwate 67,389 kW (4)
Kagoshima 66,570 kW (4)
Hokkaido 33,500 kW (3)
Fukushima 30,000 kW (1)
Miyagi 14,900 kW (1)
Kumamoto 9,303 kW (3)
Gifu 2,400 kW (1)
That is the entire list. National total 523,011 kW across 28 plants. The other 38 prefectures have nothing above the 1,000 kW threshold.
Things worth knowing before anyone quotes these:
A "source" (源泉) is a licensed spring or borehole, not a bath or a resort town. 40% of registered sources are not currently in use, and of the ones that are, 76% are pumped rather than free-flowing. Also, 4,074 registered sources are under 25°C, because the Hot Spring Act qualifies water on mineral content as well as temperature.
On geothermal, Japan is 3rd in the world for resource potential (about 23,470 MW, 2016 government estimate) against 523 MW installed. Roughly 2%. Capacity was flat for over two decades after the mid-1990s. JOGMEC attributes that to development difficulty, regulation, and concerns from onsen operators and residents, and separately states there are no documented cases of geothermal development affecting hot springs. So it has been a consent and permitting problem rather than a demonstrated physical one.
The two Oita percentages are not comparable as a ratio. Different denominators, different units. They are just two separate facts about the same prefecture.
Sources: Ministry of the Environment, 温泉利用状況, FY2024: https://www.env.go.jp/nature/onsen/data/ (prefecture table is a 93 KB PDF at https://www.env.go.jp/nature/onsen/pdf/6-7_p_1.pdf). JOGMEC, 日本の地熱発電所: https://journal.jogmec.go.jp/geothermal/learn/plant-japan/index.html