Exhibit 99.1

CALIFORNIA WATER SERVICE GROUP ANNOUNCES RESULTS FOR THE 3rd

QUARTER OF 2011 AND

RENEWAL OF HAWTHORNE LEASE

SAN JOSE, CA  —  California Water Service Group (NYSE : CWT) today announced net income of $20.9 million and earnings per common share (EPS) of $0.50 for the third quarter of 2011, compared to net income of $20.4 million and EPS of $0.49 in the third quarter of 2010.

For the quarter, total revenue increased $22.9 million, or 15.7%, to $169.3 million.  Rate increases added $21.5 million and revenue from sales to new customers added $1.0 million.  Water usage by existing customers and other changes decreased revenue by $12.8 million.  During the quarter the net change from the prior year of the water revenue adjustment mechanism (WRAM) and the modified cost balancing account (MCBA) for the third quarter 2011 was an increase of $13.2 million to revenues.   The WRAM is a ratemaking mechanism that decouples water sales from revenues and the MCBA is an account that allows California Water Service Company (Cal Water) to track and recover or refund changes in water production costs.

Total operating expenses increased by $18.7 million, or 15.5%, to $139.2 million.  Water production costs increased by $7.0 million, or 12.7%, to $61.6 million, primarily due to wholesale water rate and power cost increases that were partially offset by reduced sales to existing customers.  Administrative costs increased $3.9 million, or 21.7%, to $21.6 million, due primarily to labor & benefit expense and higher legal and outside service costs.  Other operations expenses increased $2.6 million, or 17.6%,  to $17.5 million, due to increases in planned conservation expense and water treatment and water quality expenses.

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Maintenance expense decreased $0.2 million, or 4.2%, to $4.7 million.  Depreciation expense increased $1.8 million, or 16.4%, to $12.7 million as a result of increases in capital expenditures over 2010 and updated depreciation rates adopted in the 2009 General Rate Case for Cal Water that became effective January 1, 2011.

Other income, net of income taxes, decreased $2.8 million to a net loss of $1.8 million.  Included in this number are negative mark-to-market adjustments of $2.9 million, or $0.04 per share, associated with the change in value of long-term assets held in the Company’s non-qualified retirement plans.  This compares to positive mark-to-market adjustments of $1.4 million, or $0.02 per share for the same period last year.    Interest expense increased $0.9 million, or 13.3%, to $7.3 million due to higher long-term debt interest resulting from the November 2010 debt offering, partially offset by a decrease in short-term interest due to new pricing associated with the amended unsecured line of credit.

For the twelve months ended September 30, 2011, net income was $40.7 million and diluted earnings per share were $0.98, compared to net income of $39.2 million and diluted earnings per share of $0.94 for the same period last year.  Revenues for the trailing twelve months were $504.3 million, compared to $461.9 million for the same period in the prior year.

“While the increase in volatility from the stock market affected some of our long-term, non-regulated assets, earnings from utility operations grew 16% over the third quarter of last year and 19% for the nine months ended September 30, 2011.  While we cannot control what happens in the stock market, we can control our core business, which continues to be healthy,” said President and Chief Executive Officer Peter C. Nelson.  “In addition, during the fourth quarter, we will continue to operate efficiently and recover costs of completed capital projects through the regulatory process,” added Nelson.

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Other News

Cal Water reached an agreement to operate the City of Hawthorne’s water system for another 15 years, extending a relationship that began in 1996 when Cal Water was first selected to operate and maintain the water system through a 15-year lease agreement.

“We are pleased that the City of Hawthorne has chosen to continue to have us operate and maintain its water system.  We feel the decision is a reflection of the City’s satisfaction with our service and confidence in our ability to continue to operate and maintain the water system in a professional and responsive manner,” Nelson said.

Cal Water will operate and maintain the municipal water system, which is comprised of 4 wells, 57 miles of water lines, 6 reservoirs, and a water treatment plant, and provides meter reading, billing, collections, emergency response, and other water utility services to approximately 6,000 service connections in Hawthorne.

Other Information

All stockholders and interested investors are invited to listen to the 2011 third-quarter conference call on October 27, 2011, at 11:00 a.m. (EDT), by dialing 1-888-312-3055 and keying in ID# 4591937.  A replay of the call will be available from 2:00 p.m. (EDT) October 27, 2011, through December 26, 2011, at 1-888-203-1112, ID# 4591937. The call, which will be hosted by President and CEO Peter Nelson and Vice President and Chief Financial Officer Martin A. Kropelnicki, will also be webcast under the investor relations tab at www.calwatergroup.com.

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California Water Service Group is the parent company of California Water Service Company, Washington Water Service Company, New Mexico Water Service Company, Hawaii Water Service Company, Inc., CWS Utility Services, and HWS Utility Services.  Together these companies provide regulated and non-regulated water service to nearly 2 million people in California, Washington, New Mexico, and Hawaii.  California Water Service Group’s common stock trades on the New York Stock Exchange under the symbol “CWT.”

This news release contains forward-looking statements within the meaning established by the Private Securities Litigation Reform Act of 1995 (“Act”).  The forward-looking statements are intended to qualify under provisions of the federal securities laws for “safe harbor” treatment established by the Act.  Forward-looking statements are based on currently available information, expectations, estimates, assumptions and projections, and management’s judgment about the Company, the water utility industry and general economic conditions.  Such words as expects, intends, plans, believes, estimates, assumes, anticipates, projects, predicts, forecasts or variations of such words or similar expressions are intended to identify forward-looking statements.  The forward-looking statements are not guarantees of future performance.  They are subject to uncertainty and changes in circumstances.  Actual results may vary materially from what is contained in a forward-looking statement.  Factors that may cause a result different than expected or anticipated include, but are not limited to: governmental and regulatory commissions’ decisions; changes in regulatory commissions’ policies and procedures; the timeliness of regulatory commissions’ actions concerning rate relief; new legislation; electric power interruptions; increases in suppliers’ prices and the availability of supplies including water and power; fluctuations in interest rates; changes in environmental compliance and water quality requirements; acquisitions and our ability to successfully integrate acquired companies;  the ability to successfully implement business plans; changes in customer water use patterns; the impact of weather on water sales and operating results; access to sufficient capital on satisfactory terms; civil disturbances or terrorist threats or acts, or apprehension about the possible future occurrences of acts of this type; the involvement of the United States in war or other hostilities; restrictive covenants in or changes to the credit ratings on our current or future debt that could increase our financing costs or affect our ability to borrow, make payments on debt or pay dividends; and, other risks and unforeseen events.  When considering forward-looking statements, you should keep in mind the cautionary statements included in this paragraph, as well as the Annual Report on Form 10-K, the Quarterly Reports on Form 10-Q, and other reports filed from time-to-time with the Securities and Exchange Commission (SEC).  The Company assumes no obligation to provide public updates of forward-looking statements.

Additional information is available at our web site at www.calwatergroup.com.

Attachments (2).

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CALIFORNIA WATER SERVICE GROUP

CONDENSED CONSOLIDATED BALANCE SHEETS

Unaudited

CALIFORNIA WATER SERVICE GROUP

CONDENSED CONSOLIDATED STATEMENTS OF INCOME

Unaudited

(In thousands, except per share data)