Exhibit 99.1

WGL Holdings, Inc. Reports First Quarter Fiscal Year 2013 Financial Results and

Raises Annual Dividends;

Affirms Fiscal Year 2013 Non-GAAP Guidance

Consolidated Results

WGL Holdings, Inc. (NYSE: WGL), the parent company of Washington Gas Light Company (Washington Gas) and other energy-related subsidiaries, today reported net income determined in accordance with generally accepted accounting principles in the United States of America (GAAP) for the quarter ended December 31, 2012 of $52.4 million, or $1.01 per share, compared to net income of $50.4 million, or $0.98 per share, reported for the quarter ended December 31, 2011.

Financial performance is also evaluated based on non-GAAP operating earnings (loss). Non-GAAP operating earnings (loss) excludes the effects of: (i) unrealized mark-to-market gains (losses) on energy-related derivatives for our regulated utility and retail energy marketing segments; (ii) certain gains and losses associated with optimizing the utility segment’s system capacity assets; (iii) changes in the measured value of our inventory for our wholesale energy solutions segment; (iv) the financial effects of warm or cold weather that exceeds weather protection for our regulated utility segment and (v) certain unusual transactions. Refer to “Use of Non-GAAP Operating Earnings (Loss)” and supporting reconciliations attached to this news release for a detailed discussion of management’s use of non-GAAP operating earnings, as well as reconciliations of net income determined in accordance with GAAP to non-GAAP operating earnings (loss) for both our consolidated and segment results.

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For the quarter ended December 31, 2012, non-GAAP operating earnings were $58.9 million, or $1.14 per share, compared to non-GAAP operating earnings of $58.1 million, or $1.13 per share, for the same quarter of the prior fiscal year.

Since last year, we have made certain changes to our operating segments reporting to reflect the growth of our non-utility business activities and the impact of those activities on our financial performance. All activities of WGSW, Inc. (WGSW) are now reported within the Commercial Energy Systems segment. WGSW had previously been reported within “Other Activities”. As these operations align with those of the Commercial Energy Systems segment, management has begun analyzing results and making decisions on this combined set of activities. Prior period operating segment information has been recast to reflect this new classification.

“We are happy to announce first quarter non-GAAP earnings of $1.14 per share which, in spite of a very mild start to the winter heating season, still reflect an increase over our prior year earnings” said Terry D. McCallister, Chairman and Chief Executive Officer of WGL Holdings. “Our regulated utility continues to deliver strong and predictable results, and I am pleased that several of our non-utility segments showed an increased contribution to earnings following strategic investments that we have made in recent years. Our Commercial Energy Systems segment now has 15.6 megawatts of commercial solar generating capacity on line and contributed $0.02 to per share earnings in the quarter. We believe we are on track to achieve our earnings target and are maintaining our range for non-GAAP earnings guidance.”

“I am also pleased to announce an eight-cent increase in our annual dividend to an annual rate of $1.68 per share. This 5% increase is greater than our recent average of 3%, and it reflects confidence in both our strategic plan and our ability to continue to deliver increased earnings and value to our shareholders. It also marks the 37^th consecutive year of dividend increases for shareholders of WGL Holdings and a record of uninterrupted dividends going back 162 years.”

Comparative First Quarter Results by Business Segment

Regulated Utility

For the quarter ended December 31, 2012, our regulated utility segment reported a net income of $38.7 million, or $0.75 per share, compared to net income of $44.4 million, or $0.86 per share, reported for the same quarter of the prior fiscal year. After adjustments, non-GAAP operating earnings for the regulated utility segment were $43.9 million, or $0.85 per share, for the quarter ended December 31, 2012, compared to non-GAAP operating earnings of $44.1 million, or $0.86 per share, for the same quarter of the prior fiscal year. Non-GAAP operating earnings were essentially unchanged as a result of offsetting items. Factors that lowered earnings include higher depreciation expense due to the growth in our investment in utility plant and a decrease in the recovery of carrying costs on lower average storage gas inventory balances. Factors virtually offsetting these unfavorable variances were: (i) higher revenues related to the timing of rate relief in Maryland; (ii) higher revenue due to an increase of more than 10,600 average active customer meters and (iii) a lower effective tax rate.

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Retail Energy-Marketing

For the quarter ended December 31, 2012, the retail energy-marketing segment reported net income of $13.0 million, or $0.25 per share, an increase of $12.2 million, or $0.23 per share, over net income of $0.8 million, or $0.02 per share, reported for the same quarter of the prior fiscal year. Non-GAAP operating earnings for the retail energy-marketing segment were $12.0 million, or $0.23 per share, for the quarter ended December 31, 2012, compared to non-GAAP operating earnings of $13.1 million, or $0.25 per share, for the same quarter of the prior fiscal year.

Non-GAAP operating earnings reflect lower realized electric margins due to quarterly fluctuations in the pattern of margin recognition, partially offset by increased sales volumes versus the same quarter of the prior year. Realized natural gas margins were virtually unchanged versus the same quarter of the prior year. The pattern of margin recognition that the retail energy-marketing segment realizes in a given quarter varies from year to year. Operating expenses declined due to lower customer acquisition expenses in the current quarter compared to the same quarter of the prior fiscal year.

Commercial Energy Systems

For the quarter ended December 31, 2012, the commercial energy systems segment reported net income of $1.0 million, or $0.02 per share, an increase of $0.7 million, or $0.01 per share, over net income of $0.3 million, or $0.01 per share, for the same quarter last year. The increase in earnings is due to higher revenue from commercial solar projects in the current period and higher margins on project work for government agency customers. There were no non-GAAP adjustments for this segment for any of the periods presented.

Wholesale Energy Solutions

For the quarter ended December 31, 2012, the wholesale energy solutions segment reported net income of $1.3 million, or $0.02 per share, compared to net income of $5.2 million, or $0.10 per share, for the same period of the prior fiscal year. Non-GAAP operating earnings for the wholesale energy solutions segment were $3.5 million, or $0.07 per share, an increase of $2.5 million or $0.05 per share, over non-GAAP operating earnings of $1.0 million, or $0.02 per share for the same period of the prior fiscal year. Non-GAAP operating earnings for the year were higher than in the prior year principally due to an increase in storage margins driven by the segments ongoing investments in low-cost storage capacity.

Earnings Outlook

We are updating our GAAP earnings estimate for fiscal year 2013 to a range of $2.35 per share to $2.47 per share. This estimate includes projected fiscal year 2013 earnings from our regulated utility segment in a range of $1.62 per share to $1.68 per share and projected fiscal year 2013 earnings from our unregulated business segments in a range of $0.73 per share to $0.79 per share.

We are affirming our non-GAAP consolidated earnings estimate for fiscal year 2013 in a range of $2.37 per share to $2.49 per share. This estimate includes projected fiscal year 2013 non-GAAP operating earnings from our regulated

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utility segment in a range of $1.70 per share to $1.76 per share, and projected fiscal year 2013 non-GAAP operating earnings from our unregulated business segments in a range of $0.67 per share to $0.73 per share. Refer to the “Reconciliation of GAAP Earnings Guidance to Non-GAAP Earnings Guidance” attached to this press release for a reconciliation of our GAAP earnings per share estimate to our estimate based on non-GAAP operating earnings per share.

We assume no obligation to update this guidance. The absence of any statement by us in the future should not be presumed to represent an affirmation of this earnings guidance. For the assumptions underlying this guidance, please refer to the slides accompanying our webcast that will be posted to the WGL Holdings website, www.wglholdings.com.

Other Information

We will hold a conference call at 10:30 a.m. Eastern Time on February 7, 2013, to discuss our first quarter fiscal year 2013 financial results. The live conference call will be available to the public via a link located on the WGL Holdings website, www.wglholdings.com. To hear the live webcast, click on the “Webcast” link located on the home page of the referenced site. The webcast and related slides will be archived on the WGL Holdings website through March 7, 2013.

Headquartered in Washington, D.C., WGL Holdings, Inc. has four operating segments: (i) the regulated utility segment which primarily consists of Washington Gas, a natural gas utility that serves over one million customers throughout metropolitan Washington, D.C., and the surrounding region; (ii) the retail-energy marketing segment which consists of Washington Gas Energy Services, Inc., a third-party marketer that competitively sells natural gas and electricity; (iii) the commercial energy systems segment which consists of Washington Gas Energy Systems, Inc., a provider of design-build energy efficiency solutions to government and commercial clients, commercial solar projects, and the operations of WGSW, a holding company formed to invest in alternative energy assets and (iv) the wholesale energy solutions segment which consists of Capitol Energy Ventures Corp., an asset optimization business that acquires, manages and optimizes natural gas storage and transportation assets. Additional information about WGL Holdings, Inc. is available on our website, www.wglholdings.com.

Unless otherwise noted, earnings per share amounts are presented on a diluted basis, and are based on weighted average common and common equivalent shares outstanding.

Please see the attached comparative statements for additional information on our operating results. Also attached to this news release are reconciliations of net income determined in accordance with GAAP to non-GAAP operating earnings (loss) for both our consolidated and segment results as well as reconciliations of our GAAP earnings guidance to our non-GAAP earnings guidance.

Forward-Looking Statements

This news release and other statements by us include forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 with respect to the outlook for earnings, revenues and other future financial business performance or strategies and expectations. Forward-looking statements are typically identified by words such as, but not limited to, “estimates,” “expects,” “anticipates,” “intends,” “believes,” “plans,” and similar expressions, or future or conditional verbs such as “will,” “should,” “would,” and “could.” Although we believe such forward-looking statements are based on reasonable assumptions, we cannot give assurance that every objective will be achieved. Forward-looking statements speak only as of today, and we assume no duty to update them. Factors that could cause actual results to differ materially from those expressed or implied include, but are not limited to, general economic conditions and the factors discussed under the “Risk Factors” heading in our most recent annual report on Form 10-K and other documents we have filed with, or furnished to, the U.S. Securities and Exchange Commission.

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WGL Holdings, Inc.

Consolidated Balance Sheets

(Unaudited)

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WGL Holdings, Inc.

Consolidated Statements of Income

(Unaudited)

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WGL Holdings, Inc.

Consolidated Financial and Operating Statistics

(Unaudited)

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WGL HOLDINGS, INC.

USE OF NON-GAAP OPERATING EARNINGS (LOSS)

(Unaudited)

The attached reconciliations are provided to clearly identify adjustments made to net income calculated in accordance with GAAP to derive non-GAAP operating earnings (loss). Management believes non-GAAP operating earnings (loss) provides a more meaningful representation of our earnings from ongoing operations by adjusting for the effects of: (i) unrealized mark-to-market gains and losses from energy-related derivatives for our regulated utility and retail marketing operations; (ii) certain gains and losses associated with optimizing the utility segment’s capacity assets; (iii) changes in the measured value of our inventory for our wholesale energy solutions segment; (iv) the financial effects of warmer-than-normal/colder-than-normal weather that exceeds weather protection for our regulated utility segment and (v) certain unusual transactions. This presentation facilitates analysis by providing a consistent and comparable measure to help management, investors and analysts better understand and evaluate our operating results and performance trends, and assist in analyzing period-to-period comparisons. Additionally, we use this non-GAAP measure to report to the board of directors and to evaluate management’s performance. The economic substance underlying our adjustments to calculate non-GAAP operating earnings (loss) is as follows:

We also exclude valuation adjustments to the carrying value of non-system natural gas storage inventory in our regulated utility segment. This inventory is held solely to support asset optimization transactions. Valuation adjustments to reflect lower-of-cost or market under current accounting standards may not be representative of the margins that will be realized and shared with our utility ratepayers. Non-GAAP earnings reflect actual margins realized based on the unadjusted historical cost in storage when inventory is withdrawn and sold.

There are limits in using non-GAAP operating earnings (loss) to analyze our results, as they are not prepared in accordance with GAAP and may be different from non-GAAP financial measures used by other companies. In addition, using non-GAAP operating earnings (loss) per share to analyze our earnings may have limited value as it excludes certain items that may have a material impact on our reported financial results. We compensate for these limitations by providing investors with the attached reconciliations to net income, the most directly comparable GAAP financial measure.

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WGL HOLDINGS, INC. (Consolidating by Segment)

RECONCILIATION OF GAAP NET INCOME (LOSS) TO

NON-GAAP OPERATING EARNINGS (LOSS)

(Unaudited)

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WGL HOLDINGS, INC. (Consolidated by Quarter)

RECONCILIATION OF GAAP NET INCOME (LOSS) TO

NON-GAAP OPERATING EARNINGS (LOSS)

(Unaudited)

Footnotes:

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WGL HOLDINGS, INC.

RECONCILIATION OF GAAP EARNINGS GUIDANCE TO

NON-GAAP EARNINGS GUIDANCE

FISCAL YEAR ENDING SEPTEMBER 30, 2013

Footnotes:

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