Twentieth century U.S. regulators built on an ancient common law duty that applied to public utilities such as ferries, flour mills and railroads, imposing on electric utilities a ‘‘duty to serve,’’ an obligation to provide extraordinary levels of service to customers, especially small residential customers. As applied today in most states, the public utility duty to serve entails several obligations, including: the duty to interconnect and extend service if requested; the duty to provide continuing reliable service; the duty to provide advanced notice of service disconnection; and the duty to continue service even though a customer cannot make full payment. Unlike other obligations that apply to private firms, including those such as inns and restaurants representing or holding themselves out as serving the public, in the public utility context the duty to serve requires service where it is not ordinarily considered profitable.