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): November 2, 2011

Former name or former address, if changed since last report: None

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:

¨ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

¨ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

¨ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

¨ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

On November 2, 2011, Washington Gas Light Company (Washington Gas), a subsidiary of WGL Holdings, Inc. (WGL Holdings), received an order from the District of Columbia Public Service Commission (PSC of DC) initiating an investigation into the reasonableness of Washington Gas’ base rates. Washington Gas’ last District of Columbia base rate case, filed in December 2006, was settled and became effective in December 2007. Washington Gas’ last fully adjudicated base rate case in the District of Columbia was filed in February 2003 and decided in November 2003. Washington Gas will file the required information with the PSC of DC but is not in a position at this time to determine the potential outcome of this matter.

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrants have duly caused this Report to be signed on their behalf by the undersigned hereunto duly authorized.