Exhibit 99.1

CENTERPOINT ENERGY REPORTS SECOND QUARTER 2013 EARNINGS

REAFFIRMS FULL YEAR 2013 GUIDANCE

Houston, TX – August 1, 2013 - CenterPoint Energy, Inc. (NYSE: CNP) today reported a net loss of $100 million, or $0.23 per diluted share, for the second quarter of 2013. Second quarter results included two unusual items related to the formation of the midstream partnership: (i) a $225 million, non-cash deferred tax charge and (ii) $10 million of partnership formation expenses. Excluding these items, the second quarter net income would have been $131 million, or $0.30 per diluted share. This compares to net income of $126 million, or $0.29 per diluted share, for the same period of 2012.

“The most significant accomplishment this quarter was the closing of our midstream partnership with OGE Energy, Enable Midstream Partners,” said David M. McClanahan, president and chief executive officer of CenterPoint Energy. “Our financial results for the quarter include a number of one-time charges associated with its formation. While it will take some time to realize the full potential of this new venture we remain very excited about the future of this business. Our other businesses continue to show the benefits of our balanced portfolio with our gas distribution utilities reporting a strong quarter largely offsetting the impact of milder weather on our electric utility. Operational performance continues to be very good across all of our businesses.”

For the six months ended June 30, 2013, net income was $47 million, or $0.11 per diluted share. Excluding the two unusual items noted above, net income would have been $279 million, or $0.65 per diluted share. This compares to net income of $273 million, or $0.64 per diluted share, for the same period of 2012.

Operating income for the second quarter and for the six months ended June 30, 2013, was $223 million and $555 million, respectively. CenterPoint Energy’s second quarter 2013 operating income reflects only the month of April’s results for the Interstate Pipeline and Field Services segments. Following the May 1, 2013, formation of Enable Midstream Partners, CenterPoint Energy reports its investment in midstream operations as equity income thus is not reflected in operating income. As a result, CenterPoint Energy’s operating income for the second quarter and the six months ended June 30, 2013, is not comparable to prior results.

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Electric Transmission & Distribution

The electric transmission & distribution segment reported operating income of $165 million for the second quarter of 2013, consisting of $131 million from the regulated electric transmission & distribution utility operations (TDU) and $34 million related to securitization bonds. Operating income for the second quarter of 2012 was $191 million, consisting of $153 million from the TDU and $38 million related to securitization bonds.

Economic activity around the Houston area remains robust, however second quarter operating income for the TDU declined due to milder weather. Customer growth, which continued at an annual rate of 2 percent, and higher net transmission revenues, offset increased depreciation and taxes, lower right of way revenues, and higher expenses.

Operating income for the six months ended June 30, 2013, was $249 million, consisting of $180 million from the TDU and $69 million related to securitization bonds. Operating income for the same period of 2012 was $298 million, consisting of $223 million from the TDU and $75 million related to securitization bonds.

Natural Gas Distribution

The natural gas distribution segment reported operating income of $25 million for the second quarter of 2013, compared to $9 million for the same period of 2012. Operating income benefited from colder weather as compared to last year, rate changes, and increased economic activity across our footprint, partially offset by an increase in depreciation and property taxes. Operating income also benefited from continued control of operation and maintenance expenses.

Operating income for the six months ended June 30, 2013, was $164 million, compared to $130 million for the same period of 2012.

Competitive Natural Gas Sales and Services

The competitive natural gas sales and services segment reported operating income of $3 million for the second quarter of 2013, compared to an operating loss of $4 million for the same period of 2012. Excluding the adjustments from mark-to-market accounting for derivatives associated with forward natural gas transactions used to lock in economic margin, the business performance was consistent with the prior year. Operating income for the six months ended June 30, 2013, was $10 million, compared to an operating loss of $3 million for the same period of 2012.

Other Operations

The other operations segment reported an operating loss of $10 million for the second quarter of 2013, compared to operating income of $3 million for the same period of 2012. The decline is related to the expenses associated with the formation of Enable Midstream Partners as well as higher property taxes.

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Interstate Pipelines/ Field Services

For the month of April, prior to the formation of Enable Midstream Partners, the interstate pipelines segment reported operating income of $20 million and equity earnings of $2 million from its 50 percent interest in the Southeast Supply Header (SESH) and the field services segment reported operating income of $20 million.

Midstream Investments

As previously announced, the formation of Enable Midstream Partners closed on May 1, 2013. The partnership consists of OGE’s midstream business, Enogex LLC, and CenterPoint Energy’s interstate pipelines and field services businesses, other than a 25.05 percent interest in SESH retained by the company. Following the formation of Enable Midstream Partners, CenterPoint Energy reports equity earnings from its interest in the partnership and equity earnings from its retained interest in SESH under a new midstream investments reporting segment. In May and June, CenterPoint Energy reported equity income of $33 million from its interest in Enable Midstream Partners and equity income of $2 million from its retained interest in SESH. The performance of the partnership was in line with management’s expectations given low natural gas liquids prices and low seasonal and geographic price differentials.

Dividend Declaration

On July 25, 2013, CenterPoint Energy’s board of directors declared a regular quarterly cash dividend of $0.2075 per share of common stock payable on September 10, 2013, to shareholders of record as of the close of business on August 16, 2013.

Guidance Reaffirmed for 2013

Excluding the effects of the two unusual items recorded in the second quarter related to the formation of Enable Midstream Partners as noted above, CenterPoint Energy reaffirmed its estimate for 2013 earnings on a guidance basis in the range of $1.17 to $1.25 per diluted share. Earnings guidance is being provided in the form of a range to reflect economic and operational variables associated with the company’s various business segments and ownership interest in Enable Midstream Partners and takes into consideration performance to date. Significant variables include the impact to earnings of commodity prices, volume throughput, ancillary services, weather, regulatory proceedings, effective tax rates and financing activities. In providing this guidance, the company does not include the impact of any changes in accounting standards, any impact to earnings from the change in the value of Time Warner stocks and the related ZENS securities, or the timing effects of mark-to-market and inventory accounting in the company’s competitive natural gas sales and services business.

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Filing of Form 10-Q for CenterPoint Energy, Inc.

Today, CenterPoint Energy, Inc. filed its Form 10-Q with the Securities and Exchange Commission (SEC) for the period ended June 30, 2013. A copy is available on the company’s website, under the Investors section. Company SEC filings and other documents relating to its corporate governance can also be found on the website.

Webcast of Earnings Conference Call

CenterPoint Energy’s management will host an earnings conference call on Thursday, August 1, 2013, at 10:30 a.m. Central time or 11:30 a.m. Eastern time. Interested parties may listen to a live audio broadcast of the conference call on the company’s website under the Investors section. A replay of the call can be accessed approximately two hours after the completion of the call and will be archived on the website for at least one year.

CenterPoint Energy, Inc. and Subsidiaries

Reconciliation of Net Income and diluted EPS to the basis used in providing 2013 annual earnings guidance

CenterPoint Energy, Inc., headquartered in Houston, Texas, is a domestic energy delivery company that includes electric transmission & distribution, natural gas distribution and competitive natural gas sales and services operations. The company serves more than five million metered customers primarily in Arkansas, Louisiana, Minnesota, Mississippi, Oklahoma, and Texas. The company also owns a 58.3 percent limited partner interest in Enable Midstream Partners it jointly controls with OGE Energy Corp. with operations in major natural gas and liquids-rich producing areas of Oklahoma, Texas, Arkansas and Louisiana. With more than 8,700 employees, CenterPoint Energy and its predecessor companies have been in business for more than 135 years. For more information, visit the website at www.CenterPointEnergy.com.

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This news release includes forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Actual events and results may differ materially from those expressed or implied by these forward-looking statements. The statements in this news release regarding the company’s earnings outlook for 2013 and future financial performance and results of operations, and any other statements that are not historical facts are forward-looking statements. Each forward-looking statement contained in this news release speaks only as of the date of this release. Factors that could affect actual results include (1) state and federal legislative and regulatory actions or developments affecting various aspects of CenterPoint Energy’s businesses (including the businesses of its midstream partnership with OGE Energy Corp. and affiliates of ArcLight Capital Partners, LLC (Enable Midstream Partners)), including, among others, energy deregulation or re-regulation, pipeline integrity and safety, health care reform, financial reform, tax legislation, and actions regarding the rates charged by CenterPoint Energy’s regulated businesses; (2) state and federal legislative and regulatory actions or developments relating to the environment, including those related to global climate change; (3) timely and appropriate rate actions that allow recovery of costs and a reasonable return on investment; (4) the timing and outcome of any audits, disputes or other proceedings related to taxes; (5) problems with construction, implementation of necessary technology or other issues with respect to major capital projects that result in delays or in cost overruns that cannot be recouped in rates; (6) industrial, commercial and residential growth in CenterPoint Energy’s service territories and changes in market demand, including the effects of energy efficiency measures and demographic patterns; (7) the timing and extent of changes in commodity prices, particularly natural gas and natural gas liquids, and the effects of geographic and seasonal commodity price differentials; (8) weather variations and other natural phenomena, including the impact on operations and capital from severe weather events; (9) any direct or indirect effects on CenterPoint Energy’s facilities, operations and financial condition resulting from terrorism, cyber-attacks, data security breaches or other attempts to disrupt its businesses or the businesses of third parties, or other catastrophic events; (10) the impact of unplanned facility outages; (11) timely and appropriate regulatory actions allowing securitization or other recovery of costs associated with any future hurricanes or natural disasters; (12) changes in interest rates or rates of inflation; (13) commercial bank and financial market conditions, CenterPoint Energy’s access to capital, the cost of such capital, and the results of its financing and refinancing efforts, including availability of funds in the debt capital markets; (14) actions by credit rating agencies; (15) effectiveness of CenterPoint Energy’s risk management activities; (16) inability of various counterparties to meet their obligations; (17) non-payment for services due to financial distress of CenterPoint Energy’s customers; (18) the ability of GenOn Energy, Inc. (formerly known as RRI Energy, Inc.), a wholly owned subsidiary of NRG Energy, Inc., and its subsidiaries to satisfy their obligations to CenterPoint Energy and its subsidiaries; (19) the ability of retail electric providers, and particularly the two largest customers of the TDU, to satisfy their obligations to CenterPoint Energy and its subsidiaries; (20) the outcome of litigation brought by or against CenterPoint Energy or its subsidiaries; (21) CenterPoint Energy’s ability to control costs; (22) the investment performance of pension and postretirement benefit plans; (23) potential business strategies, including restructurings, joint ventures, and acquisitions or dispositions of assets or businesses, for which no assurance can be given that they will be completed or will provide the anticipated benefits to CenterPoint Energy; (24) acquisition and merger activities involving CenterPoint Energy or its competitors; (25) future economic conditions in regional and national markets and their effects on sales, prices and costs; (26) the performance of the Midstream Partnership, the amount of cash distributions CenterPoint Energy receives from the Midstream Partnership, and the value of its interest in the Midstream Partnership, and factors that may have a material impact on such performance, cash distributions and value, including certain of the factors specified above and: (A) the integration of the operations of the businesses contributed to the Midstream Partnership with those contributed by OGE and ArcLight; (B) the achievement of anticipated operational and commercial synergies and expected growth opportunities, and the successful implementation of the Midstream Partnership’s business plan; (C) competitive conditions in the midstream industry, and actions taken by the Midstream Partnership’s customers and competitors, including the extent and timing of the entry of additional competition in the markets served by the Midstream Partnership; (D) the timing and extent of changes in commodity prices, particularly natural gas and natural gas liquids, the competitive effects of the available pipeline capacity in the regions served by the Midstream Partnership, and the

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effects of geographic and seasonal commodity price differentials, including the effects of these circumstances on re-contracting available capacity on the Midstream Partnership’s interstate pipelines; (E) the demand for natural gas, NGLs and transportation and storage services; (F) changes in tax status; (G) access to growth capital ; and (H) the availability and prices of raw materials for current and future construction projects; and (27) other factors discussed in CenterPoint Energy’s Form 10-K for the period ended December 31, 2012, as well as in CenterPoint Energy’s Quarterly Reports on Form 10-Q for the quarterly periods ended March 31, 2013, and June 30, 2013, and other reports CenterPoint Energy or its subsidiaries may file from time to time with the Securities and Exchange Commission.

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CenterPoint Energy, Inc. and Subsidiaries

Statements of Consolidated Income

(Millions of Dollars)

(Unaudited)

Reference is made to the Notes to the Consolidated Financial Statements

contained in the Quarterly Report on Form 10-Q of CenterPoint Energy, Inc.

CenterPoint Energy, Inc. and Subsidiaries

Selected Data From Statements of Consolidated Income

(Millions of Dollars, Except Share and Per Share Amounts)

(Unaudited)

Reference is made to the Notes to the Consolidated Financial Statements

contained in the Quarterly Report on Form 10-Q of CenterPoint Energy, Inc.

CenterPoint Energy, Inc. and Subsidiaries

Results of Operations by Segment

(Millions of Dollars)

(Unaudited)

Reference is made to the Notes to the Consolidated Financial Statements

contained in the Quarterly Report on Form 10-Q of CenterPoint Energy, Inc.

CenterPoint Energy, Inc. and Subsidiaries

Results of Operations by Segment

(Millions of Dollars)

(Unaudited)

Reference is made to the Notes to the Consolidated Financial Statements

contained in the Quarterly Report on Form 10-Q of CenterPoint Energy, Inc.

CenterPoint Energy, Inc. and Subsidiaries

Results of Operations by Segment

(Millions of Dollars)

(Unaudited)