Hosting capacity disclosure mandates

In September 2020, the California Public Utilities Commission (PUC) issued Decision 20-09-035, closing out the first phase of a proceeding it had opened three years earlier to overhaul the state's rules for connecting solar and storage to the grid. The decision included the requirement that California's three big investor-owned utilities would have to incorporate Integration Capacity Analysis (i.e. hosting capacity analysis) into how they evaluate interconnection requests, going further than publishing a reference map on the side.

Mandating disclosure, however, did not make the underlying data reliable. California is still working through that problem. In 2026, the CPUC approved requirements for PG&E, SCE, and SDG&E to track and remediate missing, erroneous, stale, or otherwise inaccurate ICA data and to report on discrepancies between published hosting capacity results and what the utilities found during actual interconnection reviews. Requiring utilities to publish hosting capacity doesn’t guarantee the published data is consistently usable.

Two years later, in June 2022, the commission's Energy Division issued Resolution E-5172 approving the specific tariff language PG&E, SCE, and SDG&E each filed to implement that requirement, including a 10% buffer in one of the screening steps.

Illinois’s Public Utilities Act, in section 16-105.17(f)(2)(E), requires the state's utilities to make hosting capacity analysis results, including the underlying mapping, publicly available. This is more straightforward than California’s method. It’s a statutory mandate rather than something threaded through a multiyear interconnection rulemaking.

The Minnesota PUC has driven improvements to hosting capacity disclosure through individual proceedings aimed at Xcel Energy. The PUC pushed Xcel to improve its grid transparency tools through commission orders. A statute like this stays in force until a legislature repeals it, and it doesn't automatically extend to the other utilities in the state.

Several utilities don't offer a public hosting capacity map, and where that's the case, a developer's fallback is to consult directly with the utility on a case by case basis rather. A 2024 Lawrence Berkeley National Laboratory survey of state distribution planning requirements found that only a subset of states require utilities to file any kind of distribution system plan for regulatory review, and a hosting capacity mapping requirement is a narrower than a full distribution plan, which means a state can require the planning filing without ever mandating that it show up as a public-facing map.