NYISO must refund more than $700,000, plus interest, to an energy supplier due to overcharges caused by missing meter data in the aftermath of Superstorm Sandy, the Federal Energy Regulatory Commission ruled (EL14-89) Thursday.

GDF Suez Energy Resources filed a complaint in August asking FERC to order NYISO to reopen billings for electricity supplied in November and December 2012 by Consolidated Edison to 55 Water Street, a commercial office building in lower Manhattan.

Estimated bills for the affected period, based on historical data, were off by approximately 9.7 GWh, or by more than 260%. NYISO’s Tariff bars resettlements after a five month “finalization” deadline without an order by FERC or a court.

FERC said GDF Suez should receive the refund because Superstorm Sandy caused the loss of the building’s meter data and Con Ed did not obtain the available corrected meter data until six weeks after Tariff deadlines had passed. The commission wrote that “significant injustice would result absent commission action because Suez had no recourse for the failure of Con Ed to submit corrected meter data needed for NYISO to issue corrected invoices within the required 150-day meter data finalization period.”