UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d)

OF THE SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of Earliest Event Reported): May 21, 2013

REAL GOODS SOLAR, INC.

(Exact Name of Registrant as Specified in its Charter)

833 W. South Boulder Road, Louisville, CO 80027-2452

(Address of Principal Executive Offices, Including Zip Code)

Registrant’s telephone number, including area code: (303) 222-8400

Not Applicable

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Private Placement

On May 24, 2013, Real Goods Solar, Inc., a Colorado corporation (the “Company”), entered into a Securities Purchase Agreement (the “Securities Purchase Agreement”) with unaffiliated investors identified therein (each, an “Investor” and collectively, the “Investors”), relating to a private placement by the Company of an aggregate of 3,366,974 shares of the Company’s Class A common stock (“Common Stock”), at a purchase price of $2.75 per share, or approximately $9.25 million in the aggregate, and Common Stock Purchase Warrants (“Warrants”) to purchase an aggregate of 1,683,488 shares of Common Stock with an exercise price of $2.75 per such share underlying the Warrants. The transactions contemplated by the Securities Purchase Agreement (collectively, the “Private Placement”), including the issuance of the Common Stock and the Warrants, are not a “public offering” as defined in Section 4(2) of the Securities Act of 1933, as amended (the “Securities Act”), and meet the requirements to qualify for exemption under Regulation D promulgated under the Securities Act. The closing of the Private Placement is subject to customary closing conditions and the Company and each Investor has a right to terminate the Securities Purchase Agreement if the closing has not occurred within 30 days of execution of the Securities Purchase Agreement. There can be no assurance that the Company will successfully close the Private Placement.

Upon closing of the Private Placement, the Company will issue and sell the Warrants. Each Warrant entitles the Investor to purchase 50% of the number of shares of Common Stock purchased by such Investor in the Private Placement. The Warrants will be exercisable in whole or in part, at an initial exercise price per share of $2.75 and may be exercised in a cashless exercise. The exercise price and number of shares of Common Stock issuable under the Warrants are subject to anti-dilutive adjustments, including weighted average anti-dilution protection, upon the occurrence of certain events. The Warrants may be exercised at any time upon the election of the holder, beginning on the date of issuance and ending on the fifth anniversary of the date of issuance. The Company may not issue any shares of Common Stock upon exercise of the Warrants if the issuance would exceed the aggregate number of shares of Common Stock the Company may issue in the Private Placement under applicable NASDAQ rules unless the Company first obtains shareholder approval to such issuance. The Warrants contain provisions concerning the assumption of the Warrants in connection with a Fundamental Transaction (as defined in the Warrant), and mandatory and voluntary redemption of the Warrants under certain circumstances.

Upon closing of the Private Placement, the Company will enter into a Registration Rights Agreement (the “Registration Rights Agreement”) with the Investors, which sets forth the rights of the Investors to have their shares of Common Stock purchased in the Private Placement and shares of Common Stock issuable upon exercise of the Warrants registered with the Securities and Exchange Commission (the “SEC”) for public resale under the Securities Act.

Pursuant to the Registration Rights Agreement, the Company is required to file a registration statement with the SEC (the “Registration Statement”) within 20 days of the closing of the Private Placement, registering the total number of shares of Common Stock purchased in the Private Placement and the shares of Common Stock issuable upon exercise of the Warrants. The Company will be required to have the Registration Statement declared effective within 90 days after the date of the closing of the Private Placement. The Company will also be required to maintain the effectiveness of the Registration Statement until the earlier to occur of (i) the fifth anniversary of the effectiveness of the Registration Statement or (ii) the date on which all of the registrable securities covered by the Registration Rights Agreement have been sold or transferred in a manner that they may be resold without subsequent registration under the Securities Act.

The Registration Rights Agreement further provides that in the event that (i) the Company has not filed the Registration Statement or a final prospectus within the prescribed time period, (ii) the SEC has not declared effective the Registration Statement within the prescribed time period, (iii) the Registration Statement ceases to be effective and available to the investors under certain circumstances, and (iv) the Company fails to timely file all reports required to be filed by the Company under the Securities Exchange Act of 1934, as amended, other than Current Reports on Form 8-K, the Company shall pay to the holders of registrable securities, on the occurrence of each such event and on each monthly anniversary thereof until the applicable event is cured, an amount in cash equal to 1.0% of the aggregate purchase price paid by such Investor multiplied by the percentage of such Investor’s registrable securities that are not covered by the Registration Statement, up to a maximum of 10.0% of such aggregate purchase price.

The Securities Purchase Agreement, the Registration Rights Agreement and the Warrants contain ordinary and customary provisions for agreements of this nature, such as representations, warranties, covenants, and indemnification obligations, as applicable. The foregoing descriptions of the Securities Purchase Agreement, the Warrants and the Registration Rights Agreement do not purport to describe all of the terms and provisions thereof and are qualified in their entirety by reference to the Securities Purchase Agreement, the form of Warrant and the form of Registration Rights Agreement which are filed as Exhibits 10.1, 4.1 and 10.2, respectively, to this Current Report on Form 8-K and are incorporated herein by reference.

The disclosures set forth in Item 3.02 of this Current Report on Form 8-K are hereby incorporated by reference into this Item 1.01.

Extension of Maturity Date of Loans

On May 21, 2013, the Company and Riverside Fund III, L.P. (“Riverside Fund”) extended the maturity dates of two loans in the aggregate principal amount of $3.15 million made by Riverside Fund to the Company. The maturity date of a $3.0 million loan was extended from May 4, 2014 to September 3, 2014 and the maturity date of a $150,000 loan was extended from June 20, 2014 to October 29, 2014. As amended, each loan is evidenced by a Second Amended and Restated Promissory Note, the form of which is filed as Exhibit 10.3 to this Current Report on Form 8-K.

Riverside Renewable Energy Investment LLC (“Riverside”) is a wholly-owned subsidiary of Riverside Fund. The loans were made pursuant to the terms of the Shareholders Agreement, dated as of December 19, 2011, among the Company, Riverside and Gaiam, Inc. Riverside owns approximately 29% of the Company’s currently outstanding Class A common stock and is one of our creditors. Pursuant to the terms of the Shareholders Agreement, Riverside has the right to designate a certain number of individuals for appointment or nomination to our board of directors, tied to its ownership of the Company’s Class A common stock. David Belluck, one of the Company’s directors, controls Riverside Partners III, LLC, which is the general partner of Riverside Partners III, L.P., which is the general partner of Riverside Fund.

The disclosures set forth in Item 1.01 of this Current Report on Form 8-K under the heading “Private Placement” are hereby incorporated by reference into this Item 3.02.

On May 24, 2013, the Company agreed, subject to satisfaction of certain conditions contained in the Securities Purchase Agreement, to issue and sell an aggregate of 3,366,974 shares of Common Stock and Warrants to purchase an aggregate of 1,683,488 shares of Common Stock for an aggregate purchase price of approximately $9.25 million in cash.

The investors in the Private Placement represented in writing that they were accredited investors and acquired the securities for their own accounts for investment purposes. A legend will be placed on the stock certificates stating that the securities have not been registered under the Securities Act and cannot be sold or otherwise transferred without registration or an exemption therefrom.

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Date: May 24, 2013

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