D.C. Code § 9-503
Proportionate deductions shall be made from the amounts due lighting companies for failure to furnish the illumination required by law for public lighting in the District of Columbia, and each company shall furnish, at its own expense, when and as required by the Mayor of the District of Columbia, all proper and necessary facilities, testing places, and apparatus at its plant, and such help at points on its mains or circuits as to enable the said Mayor to determine whether the required illumination is being furnished. For each and every lamp which shall be extinguished or not lighted during any portion of the scheduled time of lighting, a pro rata deduction, based upon the period of nonillumination and the price per lamp, shall be made from said amounts.
D.C. Code § 9-503