Sierra Geothermal Power Corp.
TSX VENTURE : SRA

Sierra Geothermal Power Corp.

June 17, 2008 09:00 ET

Sierra Geothermal Power's Reese River Project Reserve Estimate Doubles

VANCOUVER, BRITISH COLUMBIA--(Marketwire - June 17, 2008) -

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Sierra Geothermal Power Corp. (SGP) (TSX VENTURE:SRA) today announced the results of an independent report by GeothermEx Inc. which doubles the resource estimate on its Reese River project in Lander County, Nevada. GeothermEx estimates a 90% probability (confidence level) of generating at least 26 megawatts (net) for 20 years and a 50% probability that the reserve can support a plant of at least 58 megawatts.

GeothermEx was commissioned to conduct a geothermal resource assessment and provide an independent technical report on the Reese River project. Previously, Reese River had a 90% probability of generating 13 megawatts and 50% probability of exceeding 30 megawatts. The new estimate was based on additional exploration activities conducted by SGP. The report notes however, it is important to restate that the estimate of energy reserves is an estimate of heat in place and does not indicate that the heat can necessarily be recovered economically.

"The increased resource capacity numbers are consistent with our strategy to increase the megawatt capacity of our pipeline of projects," said Gary R. Thompson, President and CEO. "In addition to the recently announced 500% increase of the reserve estimate at Barren Hills, the improved Reese River estimates give our top five projects a combined resource capacity of approximately 150 megawatts at the 90% confidence level and 320 megawatts at the 50% confidence level. As a point of reference, a 150-megawatt geothermal power plant would provide enough clean and sustainable power for 120,000 homes."

The most recent drill results in May 2008 from Reese River include three temperature gradient wells. Wells 88-5, 62-4 and 18-33 were drilled to depths between 488 meters (1,600 feet) and 610 meters (2,000 feet). Bottom hole temperatures recorded were between 96 and 125 degrees Celsius (194 - 257 degrees Fahrenheit).

About Reese River

The Reese River project spans 25 squared kilometers (6,145 acres) in Lander County, Nevada and is located 43 kilometers (27 miles) north of Austin and 322 kilometers (200 miles) west of Reno. The Reese River geothermal target is a blind anomaly that has been independently rated as one of the top undeveloped geothermal prospects in Nevada.

Highlights of the exploration work completed to date include a total of 57 wells ranging from 100 meters to 1,500 meters in depth with recorded temperatures up to 150 degrees Celsius (302 degrees Fahrenheit). Temperature data show a large thermal anomaly that is approximately 10 kilometers long in the northeast direction by approximately 3 kilometers wide. The center of the anomaly reaches a temperature gradient of over 500 degrees Celsius per kilometer. Geophysical surveys completed to date include seismic, gravity, magnetotelluric and radiometric surveys. Geological and structural mapping has been completed and geochemical analyses were undertaken on soil, water, rock and vegetation. The Reese River project is targeted for production and power generation in 2011.

About GeothermEx

Founded in 1973, GeothermEx is the longest-established full-service geothermal consulting firm in the world. A specialist in all services related to the development of geothermal resources, GeothermEx has been involved in nearly 1,000 projects in 49 countries, working for developers, financiers, utilities, landowners and agencies of government. GeothermEx's staff consists of experts in geosciences (geology, geochemistry, geophysics, hydrology), engineering (drilling, well testing, reservoir, production, power plant, chemical), computer science and economic analysis. All have advanced degrees and many years of geothermal experience. GeothermEx has conducted due diligence and verified resource adequacy for financial institutions in nearly all geothermal projects worldwide that have been financed by bank loans or bonds. This has enabled the development of more than 6,000 megawatts of geothermal power, with the total financing to date exceeding US$10 billion. More details can be found at www.geothermex.com.

About Sierra Geothermal Power Corp.

SGP is a Vancouver-based renewable energy company focused on the exploration and development of clean, sustainable geothermal power. Geothermal power plants produce long-term stable revenues and provide continuous base-load power, often at or above 95% capacity. SGP's 17 projects comprise a total of 88,000 acres of geothermal land assets in Nevada and California. The company intends to advance the development of its portfolio of projects through a combination of equity and/or joint ventures, while continuing to evaluate additional acquisitions. To find out more about Sierra Geothermal Power Corp. (TSX VENTURE:SRA) visit our website at www.sierrageopower.com.

On behalf of the Board of Directors,

Gary Thompson, President & CEO

This news release contains forward-looking statements that are subject to certain risks and uncertainties that may cause actual results to differ materially from those projected on the basis of such forward-looking statements. Such forward-looking statements are made based upon management's beliefs, as well as assumptions made by, and information currently available to, management pursuant to the "safe-harbor" provisions of the Private Securities Litigation Reform Act of 1995.

The TSX Venture Exchange does not accept responsibility for the adequacy or accuracy of this release.

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