Dive Brief:

• Wholesale grid operators have completed their compliance filings for the Federal Energy Regulatory Commission's landmark energy storage order, setting the stage for wider participation of energy storage in wholesale markets.

• Some grid operators, such as the California ISO, have already taken steps to integrate energy storage into their markets and did not file as many changes to accommodate energy storage as other grid operators did.

• As anticipated, there are wide variances in grid operators' responses to FERC's Order 841, such as the variety of proposals from RTOs and ISOs on how to manage the charge/discharge state of a battery storage system.

Dive Insight:

FERC may have allowed the floodgates to open for energy storage when it issued Order 841 in February, but with the compliance filings in after a Dec. 3 deadline, the floodgates will likely open slowly, not suddenly.

There is not going to be a "top down" approach to energy storage accommodation, Avi Zevin, an attorney at the Institute for Policy Integrity at the New York University School of Law, told Utility Dive. In other words, FERC is not dictating a response; the responses are coming from the RTOs and they are different because each RTO or ISO has a different market structure, Zevin said.

California, arguably, is the furthest along in integrating energy storage into its market. In 2010, the state established the first energy storage target in the nation with passage of AB 2514, which established a target of 1,325 MW of energy storage by 2020 for the state's three investor-owned utilities (IOUs).

California since then has added a new target with passage of AB 2868, which calls for 500 MW of behind-the-meter storage, or 166.6 MW for each IOU. "California is furthest along and had the least changes to make," so their filing was mostly demonstrating to FERC how they are already in compliance with 841, Zevin said.

California is also different than eastern grid operators because it does not have to account for the complications of a capacity market when it is trying to accommodate energy storage. PJM, ISO New England and the New York ISO, on the other hand, all have capacity markets, but each has a different structure and different rules.

Capacity markets usually require that a resource be available for a certain minimum time. In PJM, it is 10 hours, which is difficult for most storage resources to meet. In New England, it is two hours and in New York, it is four hours.

To reduce the barrier that PJM's 10-hour requirement would impose on energy storage, the RTO has proposed allowing energy storage resources to bid in three different modes: charge, discharge and continuous. Although the categories are discrete, a resource is not locked into any single category. PJM includes a mechanism for resources to change their bid category.

That accommodation is a good example of how grid operators responded to FERC's order. "RTOs did not generally change pre-existing requirements," Zevin said. "Instead, they tended to slot storage into those pre-existing categories by making changes at the margin."

"The compliance filings are a critical step, but the major step was the issuing of Order 841," Zevin said. "Now, we are walking down the path of getting to the point where storage can participate" in wholesale power markets, he said.

The compliance filings must next go through a review and comment period at FERC. Many of the grid operators have requested specific dates by which they would like to have FERC approval, but generally the order calls for compliance with the approved rules to be in place by December 2019.

But the New York ISO has asked for a delay until May 2020. And PJM has requested that FERC allow it to run a test of the accounting changes that would have to take place to accommodate energy storage before implementing its full energy storage plan.