EXHIBIT 32.1

Certification of Chief Executive Officer and Chief Financial Officer

Pursuant to

18 U.S.C. Section 1350

as adopted pursuant to

Section 906 of The Sarbanes-Oxley Act of 2002

The undersigned, the Chief Executive Officer of Hannon Armstrong Sustainable Infrastructure Capital, Inc. (the “Company”), hereby certifies to the best of his knowledge on the date hereof, pursuant to 18 U.S.C. 1350(a), as adopted pursuant to Section 906 of The Sarbanes-Oxley Act of 2002, that the Quarterly Report on Form 10-Q for the quarter ended March 31, 2014 (the “Form 10-Q”), filed concurrently herewith by the Company, fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended, and that the information contained in the Form 10-Q fairly presents, in all material respects, the financial condition and results of operations of the Company.

Date: May 13, 2014	By:	/s/ Jeffrey W. Eckel
		Name:	Jeffrey W. Eckel
		Title:	Chairman, Chief Executive Officer and President

The undersigned, the Chief Financial Officer of Hannon Armstrong Sustainable Infrastructure Capital, Inc. (the “Company”), hereby certifies to the best of his knowledge on the date hereof, pursuant to 18 U.S.C. 1350(a), as adopted pursuant to Section 906 of The Sarbanes-Oxley Act of 2002, that the Quarterly Report on Form 10-Q for the quarter ended March 31, 2014 (the “Form 10-Q”), filed concurrently herewith by the Company, fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended, and that the information contained in the Form 10-Q fairly presents, in all material respects, the financial condition and results of operations of the Company.

Date: May 13, 2014	By:	/s/ J. Brendan Herron
		Name:	J. Brendan Herron
		Title:	Chief Financial Officer and Executive Vice President

Pursuant to the Securities and Exchange Commission Release 33-8238, dated June 5, 2003, this certification is being furnished and shall not be deemed filed by the Company for purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or incorporated by reference in any registration statement of the Company filed under the Securities Act of 1933, as amended.

A signed original of this written statement required by Section 906 has been provided to the Company and will be retained by the Company and furnished to the Securities and Exchange Commission or its staff upon request.