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PUC hears sharp disagreement over NEM Plus battery-to-solar ratio; industry urges rapid resolution
Summary
Parties debating amendments to the NEM Plus tariff differed sharply over a proposed PV-to-battery size ratio. Hawaiian Electric raised concerns the DER-party ratio could be insufficient for grid services; DER representatives said the utility's 1:2 PV-to-battery ratio is a nonstarter and urged the commission to approve flexible rules quickly.
The Public Utilities Commission heard extended debate over proposed amendments to the Net Energy Metering Plus (NEM Plus) tariff, with disagreement concentrating on the permissible ratio of photovoltaic (PV) capacity to battery capacity for customers seeking to add storage to existing NEM systems.
Hawaiian Electric raised concerns that a DER-party–favoring ratio could leave too little PV to reliably charge batteries for grid services; Rocky Mould and other DER-party representatives said modeling is under way but argued that overly restrictive ratios would make new systems uneconomic and prevent customer participation in grid-service programs.
“It's difficult for the 1 to 2 ratio that HECO has presented ... to meet the grid service needs,” Rocky Mould said, summarizing modeling concerns. Industry participants said a utility-imposed 1 kW PV to 2 kW battery ratio (utility wording) is unlikely to produce a viable market; Steve Rimshaw said the proposed HECO ratio is “a nonstarter” and “no one's gonna economically do this.”
DER parties indicated they are running additional use-case modeling and signaled openness to compromise; Rocky said the DER parties remain amenable to the green items in HECO’s slide and that modeling results would be provided quickly. HECO said it will continue to work with parties and that parties should bring specific data if they believe a different ratio is necessary.
Several participants and the Consumer Advocate asked for use-case modeling showing export or curtailment impacts. HECO and DER representatives discussed whether excess PV would serve on-site load, charge EVs, or be curtailed; parties said controls at the point of interconnection would limit exports to the system’s original NEM capacity and permit coordinated participation in grid services.
Commissioners urged the parties to agree quickly where possible; if not, commissioners said they expect focused briefs on the unresolved ratio question so the commission can decide. No tariff change was adopted at the conference.
