U.S. Geothermal Updates El Ceibillo Project

BOISE, IDAHO--(Marketwired - Oct. 28, 2015) - (TSX:GTH)(NYSE MKT:HTM) U.S. Geothermal Inc. (the "Company"), a leading renewable energy company focused on the development, production, and sale of electricity from geothermal energy, is pleased to announce that its whole owned subsidiary U.S Geothermal Guatemala S.A. has completed the drilling of well EC-2A and that well has successfully intersected a commercial geothermal resource at its El Ceibillo project in Guatemala.

The resource found in well EC-2A was intersected at a depth of 1,300 feet (396 meters) and had a flowing temperature of 389°F (198.5°C). This well was drilled to follow up on a 2014 temperature gradient drilling program in which two shallow wells also found high temperature fluid, but not in commercial quantities. Temperature gradient well TG-6 recorded a fluid temperature of 372°F (189°C) at 558 feet (170 meters) and well TG-7 found fluid at 381°F (194°C) at 659 feet (201 meters) deep.

Additionally, as previously announced, the Guatemalan Ministry of Energy and Mines had approved the modified project schedule that is included in our concession agreement on July 21, 2015. The modified project schedule was updated in the concession agreement and was approved October 13, and the Minister of Energy and Mines signed the final decree approving the modified concession agreement.

"We are extremely pleased with the results of this well, discovering geothermal fluids with both high temperature and in commercial quantities" said Dennis Gilles, Chief Executive Officer. "We are additionally pleased and grateful to the Minister of Energy and Mines, for providing the final approval of our modified concession agreement. Our goal now is to continue to expand the reservoir area, and define the expected size of the project so we can move forward to secure a Power Purchase Agreement and start construction."

Based on the discovery at EC-2A, two additional wells have been sited to further extend the resource area to the south and west of the known high temperature permeability and to test a deeper horizon in the system. Drill pads are being constructed and drilling of the next well is expected to begin within the next few weeks as weather allows. Pending results of these two wells, a decision will be made on the location for a production size well to fully test the resource to determine its size and production characteristics.

About U.S. Geothermal Inc.:

U.S. Geothermal Inc. is a leading and profitable renewable energy company focused on the development, production and sale of electricity from geothermal energy. The company is currently operating geothermal power projects at: Neal Hot Springs, Oregon, San Emidio, Nevada and Raft River, Idaho for a total power generation of approximately 45 MWs. The company is also developing projects at: The Geysers, California; a second phase project at San Emidio, Nevada; the El Ceibillo project located near Guatemala City, Guatemala; and at Crescent Valley, Nevada. U.S. Geothermal's growth strategy is to reach 200 MWs of generation by 2020 through a combination of internal development and strategic acquisitions.

Please visit our Website at: http://www.usgeothermal.com

The information provided in this news release may contain forward-looking statements within the definition of the Safe Harbor provisions of the US Private Securities Litigation Reform Act of 1995. Readers are cautioned to review the risk factors identified by the company in its filings with US and Canadian securities agencies. All statements, other than statements of historical fact, included herein, without limitation, statements relating to the future operating or financial performance of U.S. Geothermal, are forward-looking statements. Forward-looking statements are frequently, but not always, identified by words such as "expects", "anticipates", "believes", "intends", "estimates", "potential", "possible", and similar expressions, or statements that events, conditions, or results "will", "may", "could", or "should" occur or be achieved. These forward-looking statements may include statements regarding perceived merit of properties; interpretation of the results of well tests; project development; resource megawatt capacity; capital expenditures; timelines; strategic plans; or other statements that are not statements of fact. Forward-looking statements involve various risks and uncertainties. There can be no assurance that such statements will prove to be accurate, and actual results and future events could differ materially from those anticipated in such statements. Important factors that could cause actual results to differ materially from U.S. Geothermal's expectations include the uncertainties involving the availability of financing in the debt and capital markets; uncertainties involved in the interpretation of results of well tests; the need for cooperation of government agencies in the development and operation of properties; the need to obtain permits and governmental approvals; risks of construction; unexpected cost increases, which could include significant increases in estimated capital and operating costs; and other risks and uncertainties disclosed in U.S. Geothermal's Annual Report on Form 10-K for the year ended December 31, 2014 filed with the United States Securities and Exchange Commission and Canadian securities regulatory authorities and in other U.S. Geothermal reports and documents filed with applicable securities regulatory authorities from time to time. Forward-looking statements are based on management's expectations, beliefs and opinions on the date the statements are made. U.S. Geothermal Inc. assumes no obligation to update forward-looking statements if management's expectations, beliefs, or opinions, or other factors, should change.

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