Binding tariffs and voluntary hosting capacity maps

About 20 states require their electric utilities to file a distribution system plan with the state commission for review, according to a 2024 Lawrence Berkeley National Laboratory report on state distribution planning requirements. That leaves 30 that aren’t obligated to.

A companion PNNL-authored table from the same research program lists "voluntary distribution or grid modernization plans" as its own row among rows for hosting capacity analysis requirements, storm hardening requirements, and non-wires alternatives requirements.

Tariffs A tariff is the utility's filed rate schedule, which encompasses the prices, the customer classes, the rules for billing, disconnection, and everything else that governs how service is provided. Once a state commission approves it, public utility commissions and legal commentary alike describe it as carrying the force and effect of a contract between the utility and its customers. A tariff is the document a utility is legally bound to charge and operate by until it's changed through another approved filing.

Rate cases A rate case is how a tariff changes. New York's Department of Public Service’s rate case overview page states that the commodity cost of electricity or gas is set by the market and isn't something the commission regulates, but delivery rates (everything the utility charges to own, operate, and maintain the wires and pipes themselves) are established through "a formal legal process referred to as a rate case." A rate case is a proceeding, not a document, in which a utility files an application to raise its revenue, intervenors get a chance to challenge the numbers, staff and the utility exchange testimony, and the outcome (approved as-filed, negotiated down through a settlement, or rejected) becomes the new tariff once the commission signs off.

In Illinois, the Public Utilities Act requires utilities to make hosting capacity analysis results publicly available. But in a state without an equivalent requirement, the costs of planning only get recovered from customers (i.e. the utility only gets paid) once they pass through a rate case according to R Street. The voluntary disclosure is useful, but it does hold a lower level of accountability than the other two categories.