(Bloomberg) -- The independent market monitor for the Texas power grid recommended capping the price of so-called ancillary services during the week the state suffered blackouts due to a severe winter storm.

Potomac Economics said the cap should be set at $9,000 a megawatt-hour for Feb. 15 through Feb. 20, in line with the price of power during the period, according to a letter submitted to the Public Utility Commission of Texas.

Because the real-time price of electricity was already set at the $9,000 cap during the grid emergency, the cost of ancillary services skyrocketed, costing some companies tens of millions of dollars. Some power retailers have asked the utility commission to waive their obligation to pay those high charges while their challenges are ongoing.

Ancillary services help the grid operator maintain reliability on the system, including by infusing the grid with quick bursts of energy that stabilize the flow of electricity.

The market monitor also said that market participants shouldn’t have to pay for ancillary services that weren’t provided during the grid emergency. Ercot operators failed to note when these services weren’t being delivered due to outages, resulting in charges, the monitor said.

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