History
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| June 1946 | Nippon Koei (Shinko Power Co., Ltd) is established. |
|---|---|
| Kawasaki Plant is established. | |
| June 1947 | Haneda Plant is established. |
| May 1952 | Kamata Plant is established. |
| Haneda Plant closed. | |
| Kawasaki Plant is established. | |
| Apr 1958 | Nikki Manufacturing Co., Ltd. is established. |
| Setagaya Plant is established. | |
| Aug 1963 | Yokohama Plant is established. |
| Jan 1969 | Kamata Plant abolished. |
| Jan 1975 | The Manufacturing Dept. transferred from Nikki Manufacturing. |
| July 1977 | The No.1 building at the Yokohama Plant is completed. |
| June 1979 | The No.3 building at the Yokohama Plant is completed. |
| Apr 1981 | The No.4 building at the Yokohama Plant is completed. |
| Oct 1986 | Koei System is established. |
| Dec 1988 | The No.2 building at the Yokohama Plant is completed. |
| Jan 1993 | The No.5 and No.6 building at the Yokohama Works completed. |
| Apr 1998 | Nippon Koei Yokohama Works Co., Ltd. (Renamed to NKPS in 2001) is established. |
| Jan 2002 | Fukushima Works by NKPS is established. |
| May 2002 | The Transmission line Dept is splitting. |
| Apr 2010 | NKPS is reintegrated into Nippon Koei. |
| Jan 2015 | KOEI Energy Co., Ltd. is established. |
| Dec 2018 | Nippon Koei Energy Europe.B.V.（NKEE）in Rotterdam, Netherlands is established. |
| Apr 2023 | Nippon Koei Energy Solutions Co., Ltd. is established. |
| Oct 2023 | Nippon Koei Energy Solutions Co., Ltd. is established. (reconstruction). |
