History
| May 1979 | Established Hanwa Nessui Ind. Co., Ltd., origin of TESS Engineering |
|---|---|
| January 1992 | Changed name to TESS Engineering Co., Ltd. |
| November 1999 | Opened 24 Hours Operation Monitoring System |
| July 2000 | Acquired ISO14001 - Environmental Management System |
| February 2006 | Gas Engine driven 70 MW Co-Generation Power Plant Started O & M total service business |
| February 2007 | Registered in "FY2006 Voluntary Participating Domestic Discharge Amount Trading System" promoted by Ministry of Environment（including 2007） |
| December 2008 | Participated in Trial Discharge Amount Trading Scheme |
| May 2009 | Registered as company granted "Green Power Certificate" - Renewable Energy Certificate |
| July 2009 | Masayuki Ishiwaki assumed Chairman, and Hideo Ishiwaki assumed President of the company Established TESS Techno Service Co., Ltd. Selected as trustee for "FY2009 Domestic Credit System - Soft Supporting Business" promoted by METI (including 2010) |
| February 2010 | Applied "Power Producer and Supplier" to METI (Ministry of Economy, Trade and Industry) |
| 2011 | Contributed for construction of captive power plants at various factories and offices to cover the consequent power shortage by Great East Japan Earthquake |
| 2012 | Executed many EPC contracts on solar and biomass power plants as FIT (Feed-in Tariff System) enacted in Japan |
| March 2012 | Established Intelligent Solar Systems Co., Ltd. |
| March 2013 | Established Prime Solar LLC |
| June 2013 | Strated operation of "TESS Tokushima-Anan Solar Power Station" as own power business Developing own power plants throughout Japan |
| April 2014 | Established TESS Asset Management LLC |
| June 2014 | Established T&M Solar LLC |
| December 2014 | Acquired ISO9001 - Quality Management System Acquired ISO27001 - Information Security Management System |
| November 2015 | Registered as electricity retailer |
| April 2017 | Accumulated construction job records of Solar Power Stations based on FIT (Feed-in Tariff) exceed more than 430MW |
| July 2017 | Hideo Ishiwaki assumed Representative Director and Chairman, and Toshihiro Takasaki assumed Representative Director and President. |
| April 2018 | Company shifts to holding company structure,with TESS Holdings Co., Ltd. as parent company |
| March 2020 | PT PTEC Research and Development established to conduct research and development in biomass fuel manufacturing |
| August 2020 | VT Utilities Services K.K. established through joint venture with Veolia Japan K.K. |
| February 2021 | Combined generation capacity of renewable energy power plants owned by TESS Group tops 200 MW |
| April 2021 | TESS Holdings lists on Tokyo Stock Exchange First Section(currently Prime Market) |
| July 2025 | Tokyo Branch is renamed Tokyo Head Office, and the company transitions to a dual head office system with the Osaka Head Office. |
