Dive Brief:

• The Federal Energy Regulatory Commission on April 1 asked regional grid operators for more information on how they will implement a major order on energy storage issued last year.

• FERC asked each grid operator to detail various aspects of energy storage market participation, including size requirements, state of charge management and how storage resources can participate as both buyers and sellers in wholesale markets.

• The requests come as FERC considers rehearing requests on its landmark February 2018 energy storage directive, Order 841. Grid operators have 30 days to file responses.

Dive Insight:

FERC's April 1 letters to regional grid operators are the latest development on Order 841, which has yet to be finalized more than a year after its unanimous approval.

Last February, FERC directed regional grid operators to devise new tariffs for storage market participation that allow the resources to provide multiple electricity market services, as well as set power market prices as purchasers and sellers of energy. 

The nation's regional transmission organizations and independent system operators filed their responses in December, detailing a wide range of tariff changes for storage participation.

Many energy storage backers, however, saw the filings as incomplete. At the time, analysts told Utility Dive that many of the grid operators are "leaving some required pieces out" of their orders.

Storage officials also expressed concern about a number of particular proposals, including a 10-hour discharge requirement for storage to participate in PJM's capacity market and various aspects of the New York ISO's proposal.

On April 1, FERC asked for more detail from each operator, issuing deficiency letters to all six RTOs and ISOs under its jurisdiction.

The letters vary by region, but each hits on a series of basic questions, including physical and operational characteristics, charging requirements and metering, as well as the ability of storage to participate as both load and generation in wholesale markets.

Storage industry officials and allies welcomed the letters, saying they appear to address some of the sector's concerns with the original compliance filings.

"[O]n a quick skim they demonstrate that FERC is looking for real compliance with the [requirements] to open the markets to storage, and not just paper compliance," Jeff Dennis, general counsel at trade group Advanced Energy Economy, said on Twitter.

FERC has yet to rule on rehearing requests for Order 841, but the letters show the commission is moving forward with implementation. Environmental advocates joined the storage industry's praise of FERC's move.

"For example, FERC asks PJM whether a Capacity Storage Resource is included in the definition of a Generation Capacity Resource under its Handbook - pushing back on PJM's basis for the 10 hour requirement," tweeted Kim Smaczniak, a clean energy attorney at Earthjustice. "So I read this as a very positive development for Order 841 implementation!"