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.