Exhibit 99.1

Hannon Armstrong Announces 35% Increase in Q1 2015 Core Earnings to $0.27 per Share

ANNAPOLIS, Md., May 6, 2015 /PRNewswire/ — Hannon Armstrong Sustainable Infrastructure Capital, Inc. (“Hannon Armstrong,” “we,” “our” or the “Company;” NYSE: HASI), a leading provider of debt and equity financing to the energy efficiency and renewable energy markets, today reported Core Earnings, a non GAAP financial measure, for the quarter ended March 31, 2015, of $7.4 million or $0.27 per share, an increase of 35% over the $0.20 per share in the same quarter last year.

On a GAAP basis, the Company recorded net income for the quarter ended March 31, 2015 of $2.1 million or $0.07 per share as compared to a $2.8 million or $0.17 per share in the same quarter in 2014. A reconciliation of our Core Earnings to GAAP net income is included in this press release.

“2015 has started stronger than 2014 and our pipeline for the rest of the year is robust with growth in the efficiency, wind and solar asset classes,” said CEO Jeffrey Eckel. “With the completion of our recent equity offering, we look forward to continuing to invest our new capital to support our sustainable yield returns.”

Highlights

Portfolio

Our Portfolio totaled $885 million at March 31, 2015 and included $306 million of energy efficiency investments, $537 million of renewable energy (wind and solar) transactions and $42 million of other sustainable infrastructure investments. The following is an analysis of our Portfolio by type of obligor and credit quality as of March 31, 2015, with 98% of the Debt and Real Estate portion of the Portfolio rated investment grade as shown below:

First Quarter Financial Results

Hannon Armstrong reported first-quarter Core Earnings of $7.4 million or $0.27 per share, as compared with Core Earnings of $3.4 million, or $0.20 per share, in Q1 2014. The increase in Core Earnings is largely due to an increase in Core Net Investment Revenue, which increased to $7.6 million from $2.4 million in Q1 2014 due to an 82% growth in the Portfolio from Q1 2014. This increase was offset by a decrease in other investment revenue of $0.2 million and an increase of $1.0 million in Core Other Expenses, net to $3.3 million from $2.3 million in Q1 2014. Core Other Expense rose due to an increase in personnel and G&A expenses related to the growth in the business.

As of March 31, 2015, we had 39% of our debt at fixed rates as shown in the chart below:

As of March 31, 2015, leverage, as measured by debt-to-equity, was 2.0 to 1. This calculation excludes securitizations that are not consolidated on our balance sheet (where the collateral is typically borrowings with U.S. government obligors) and our on balance sheet match funded nonrecourse debt.

“The combination of our key growth drivers of an increasing investment portfolio, margin expansion and operating leverage from an internally managed platform all contributed to our strong performance in the quarter,” said Chief Financial Officer Brendan Herron. “Having completed the equity raise in April, we are focused on putting the capital to work while executing on our plan to achieve our increased targets for financial leverage and fixed-rate debt financing.”

Conference Call and Webcast Information

Hannon Armstrong will host an investor conference call today at 5:00 pm ET. Interested parties are invited to listen to the conference call by dialing 1-877-407-0784, or for international callers, 1-201-689-8560. A replay will be available two hours after the call and can be accessed by dialing 1-877-870-5176, or for international callers, 1-858-384-5517. The passcode for the live call and the replay is 13608851. The replay will be available until May 13, 2015. A webcast of the conference call will also be available through the Investor Relations section of our website, at www.hannonarmstrong.com.

A copy of this press release is also available on our website.

About Hannon Armstrong

We provide debt and equity financing to the energy efficiency and renewable energy markets. We focus on providing preferred or senior level capital to established sponsors and high credit quality obligors for assets that generate long-term, recurring and predictable cash flows. We are based in Annapolis, Maryland, and we elected and qualified to be taxed as a real estate investment trust (“REIT”) for federal income-tax purposes, beginning with our taxable year ended December 31, 2013.

Forward-Looking Statements

Some of the information contained in this press release are forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. When used in this press release, the words such as “believe,” “expect,” “anticipate,” “estimate,” “plan,” “continue,” “intend,” “should,” “may,” “target,” or similar expressions, are intended to identify such forward-looking statements. Forward-looking statements are subject to significant risks and uncertainties. Investors are cautioned against placing undue reliance on such statements. Actual results may differ materially from those set forth in the forward-looking statements. Factors that could cause actual results to differ materially from those described in the forward-looking statements include those discussed under

the caption “Risk Factors” included in our most recent Annual Report on Form 10-K filed with the U.S. Securities and Exchange Commission, as well as in other reports that we file with the SEC. Those factors include:

Forward-looking statements are based on beliefs, assumptions and expectations as of the date of this press release. We disclaim any obligation to publicly release the results of any revisions to these forward-looking statements reflecting new estimates, events or circumstances after the date of this earnings release.

The risks included here are not exhaustive. Additional factors could adversely affect our business and financial performance. Moreover, we operate in a very competitive and rapidly changing environment. New risk factors emerge from time to time and it is not possible for management to predict all such risk factors, nor can we assess the impact of all such risk factors on our business or the extent to which any factor, or combination of factors, may cause actual results to differ materially from those contained in any forward-looking statements. Given these risks and uncertainties, investors should not place undue reliance on forward-looking statements as a prediction of actual results.

Investor Relations 

410-571-6189

investors@hannonarmstrong.com

EXPLANATORY NOTES

Non-GAAP Financial Measures

Core Earnings

Core Net Investment Revenue, Core Total Revenue, Core Other Expenses, net and Core Earnings (“Core Financial Metrics”) are non-GAAP financial measures. Core Net Investment Revenue reflects the wind equity investments adjusted to an effective interest method and the add back of non-cash real estate intangible amortization and the provision for credit losses, if any.

Our equity method investment in the wind projects is structured in a wind partnership “flip” structure where we, along with a number of other institutional investors, receive a pre-negotiated preferred return consisting of a priority distribution from the project cash flows along with tax attributes. Once this preferred return is achieved, the partnership flips and the project owner receives the majority of the cash flow with the institutional investors retaining an ongoing residual interest. Given this structure, we negotiated our purchase price of this investment based on our assessment of the expected cash flows from this investment discounted back to net present value based on a discount rate that represented an expected yield on the investment. This is similar to how we value the expected cash flows in financing receivables. Under U.S. GAAP, we are required to account for this investment utilizing the hypothetical liquidation at book value method (“HLBV”), in which we recognize income or loss based on the change in the amount each partner would receive if the assets were liquidated at book value, in this case, at the end of the immediately preceding quarter after adjusting for any distributions or contributions made during such quarter. As HLBV incorporates non-cash items, such as depreciation, and because we are entitled to receive a preferred return of cash flows on our investment independent of how profits and losses are allocated, the HLBV allocation does not, in our opinion, reflect the economics of our investment. As a result, and in an attempt to treat these investments in a manner similar to our other investments and our initial valuation, in calculating our Core Net Investment Revenue for the above periods, we adjusted the income we receive from this investment as if we were recognizing income or loss based on an effective interest methodology. Generally, under this methodology income is recognized over the life of the asset using a constant effective yield. The initial constant effective yield we selected is equal to the discount rate we used in making our investment decision. On at least a quarterly basis, we will review and, if appropriate, adjust this discount rate and the income or loss we receive from this investment for purposes of calculating our Core Net Investment Revenue in future periods, as necessary, to reflect changes in both actual cash flows received and our estimates of the future cash flows from the projects. We borrowed $115 million on a nonrecourse basis using this $144 million equity method investment as collateral. For the three months ended March 31, 2015, we collected cash distributions from the wind investment of $6.3 million and included in our U.S. GAAP investment interest expense was $1.7 million of interest expense related to the loan on this investment.

Core Other Expenses, net reflects the add back of non-cash equity-based compensation, amortization of intangible assets, GAAP HLBV income or loss on our equity method investment, and business acquisition costs, if any. Core Earnings represent earnings utilizing the adjustments for Core Net Investment Revenue and Core Other Expenses, net plus adjusting for any non-cash taxes and the minority interest. Our Core Financial Metrics are also adjusted to exclude one-time events pursuant to changes in GAAP and certain other non-cash charges, if any, as approved by a majority of our independent directors.

We believe that the Core Financial Metrics provide an additional measure of our core operating performance by eliminating the impact of certain non-cash income and expenses and facilitating a comparison of our financial results to those of other comparable REITs with fewer or no non-cash charges and a comparison of our operating results from period to period. Our management uses Core Financial Metrics in this way. We believe that our investors also use our Core Financial Metrics or a comparable supplemental performance measure to evaluate and compare our performance to our peers, and as such, we believe that the disclosure of our Core Financial Metrics is useful to our investors.

Core Earnings does not represent cash generated from operating activities in accordance with GAAP and should not be considered as an alternative to net income (determined in accordance with GAAP), or an indication of our cash flows from operating activities (determined in accordance with GAAP), a measure of our liquidity or an indication of funds available to fund our cash needs, including our ability to make cash distributions. In addition, our methodology for calculating our Core Financial Metrics may differ from the methodologies employed by other REITs to calculate the same or similar supplemental performance measures, and accordingly, our reported Core Earnings may not be comparable to the Core Earnings reported by other REITs.

The table below provides a reconciliation of the GAAP Net Investment Revenue, net to Core Net Investment Revenue:

The table below provides a reconciliation of the GAAP Other Expenses, net to Core Other Expenses, net:

We calculated our Core Earnings and provided a reconciliation of our net income to Core Earnings in the table below:

HANNON ARMSTRONG SUSTAINABLE INFRASTRUCTURE CAPITAL, INC.

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

(AMOUNTS IN THOUSANDS, EXCEPT SHARE AND PER SHARE DATA)

HANNON ARMSTRONG SUSTAINABLE INFRASTRUCTURE CAPITAL, INC.

CONDENSED CONSOLIDATED BALANCE SHEETS

(AMOUNTS IN THOUSANDS, EXCEPT SHARE AND PER SHARE DATA)