IREC guide aims to help states deploy solar hosting capacity maps


Solar hosting capacity maps have been called “treasure maps” for solar developers as they show which portions of distribution circuits can accommodate more solar installations without costly circuit upgrades.

More states are set to join the nine states that already require utilities to provide the maps, which help to speed up the most cost-effective solar installations. But states that have already embraced hosting capacity maps faced bumps along the way, including delays that can last for years.

To smooth the path for states that are just beginning to implement requirements, as well as states that want to improve existing maps, the Interstate Renewable Energy Council (IREC) published a guide, “Key Decisions for Hosting Capacity Analyses.”

IREC’s guide advises states to start by involving stakeholders and defining the use cases that the maps must serve. The guide describes 12 more high-level decision points for states as they work to achieve useful hosting capacity maps.

The first iteration of maps could be based on a modest set of state requirements, said the guide. Later iterations could specify additional functionality. A map that shows why hosting capacity is limited in a given location, for example, will let a customer see whether redesigning the project, perhaps with energy storage or a smart inverter, will address the capacity limitation.

Maps also could show locations where a distributed resource may provide a system benefit. Over time, the maps could guide deployment not just of solar but also storage, electric vehicle chargers, and heat pumps.

IREC said that while it has opinions on preferred ways of approaching each of the regulatory decision points, its guide aims to present options and their implications, rather than expressly advocate for any given approach. The guide reflects IREC’s insights from numerous state proceedings on hosting capacity maps.

California’s lessons

The guide describes California’s “rocky rollout” of its integration capacity analysis tool—the state’s name for hosting capacity analysis—as all three investor-owned utilities showed in 2019 that anywhere from 60-80% of their distribution systems had little to no load hosting capacity. Discussions among stakeholders and regulators led to the conclusion that the results were erroneous, the guide said.

California then set data validation requirements for each utility. It also invited stakeholders to comment on the utilities’ data validation plans, and hired an independent expert to review the plans.

Regulators in other jurisdictions have the opportunity to begin oversight of data validation earlier in the hosting capacity analysis process, the guide said.

IREC noted that some early decisions can be “difficult, expensive, or time-intensive” to change after the fact, while others “can be built upon and evolve along with the analysis over time.”

A growing trend

Illinois and Colorado recently ordered their utilities to provide hosting capacity analyses, said IREC staff. Several other states are having regulatory discussions about requiring the analyses or improving existing ones, including Oregon, New Mexico, Ohio, and New Hampshire.

Those states join at least seven others that already require hosting capacity analyses: California, Nevada, Minnesota, New York, Maryland, New Jersey, and Connecticut.

And in at least seven more states, at least one utility provides hosting capacity maps. Those states are Hawaii, Michigan, Virginia, North Carolina, Vermont, Massachusetts, and Rhode Island, according to IREC staff and our previous coverage. In Georgia, solar groups have called for hosting capacity maps, while in Maine two citizens groups have done the same.

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