MISO has made another attempt to coax more time from FERC to calculate refunds to transmission customers over the commission’s ever-changing return on equity percentage.

The RTO has now asked for an extension until May 31 to complete the refunds (EL14-12-004).

The grid operator previously requested a June 30 deadline to determine refund amounts; FERC granted a delay until Feb. 28 from its original Sept. 23, 2021, deadline to calculate the reimbursements. (See MISO, TOs: More Time Needed for ROE Refunds.)

MISO said it has good cause to support a spring deadline, saying the “overall resettlement task remains unchanged” since it first requested an extension. The RTO said it and its transmission owners have completed resettlements from 2013 to 2019, but said the remaining refunds require a more complex calculation that relies on forward-looking transmission rates and true-up mechanisms.

The grid operator said it expects to crunch numbers through April, with transactions to take place in May. MISO Senior Manager of Transmission Settlements Christina Drake said it remains “infeasible to implement all of the directed refunds within the timeframe set forth by the commission’s orders.” It promised the refunds will include interest at FERC-approved rates.

MISO said as an example, 2020’s refunds involve 103 transmission owners and “all charges made under related tariff schedules and attachments that use those parties’ ROE, including the systemwide average rate for through-and-out service.”

The RTO’s extensive refund calculations stem from a return on equity that FERC changed several times over a handful of years as it tried to nail down an appropriate baseline for investors backing transmission projects.

The commission in 2020 enacted a 10.02% ROE for transmission rates effective Sept. 28, 2016, superseding the 9.88% and 10.32% ROEs approved in 2019 and 2016, respectively. Those figures were at different times intended to replace the 12.38% ROE established in 2002, which FERC deemed excessive almost a decade ago. In all, MISO TOs must pay refunds for the period of November 2013 to February 2015 and September 28, 2016, to December 23, 2020. (See FERC Ups MISO TO ROE, Reverses Stance on Models.)