PBR regulation is best conceptualized as a continuum, ranging from “soft” to “hard” mechanisms, rather than as a single type of regulatory regime. “Soft” mechanisms include relatively minor adaptations to the traditional COS framework, such as regulatory lags (where rates may be fixed for a period of time) and efficiency audits and reviews. In contrast, price caps and revenue caps (where prices or revenues adjust annually for inflation minus targeted productivity improvements) are “harder” forms of PBR. Performance standards and earnings sharing mechanisms, between customers and the regulated utility, lie in the middle of the continuum.