United Illuminating | 6,154 followers on LinkedIn. United Illuminating (UI) is a New Haven-based regional electric distribution company established in 1899. UI is engaged in the purchase, transmission, distribution and sale of electricity and related services to more than 341,000 residential, commercial and industrial customers in the Greater New Haven and Bridgeport areas. At UI, we've always been dedicated to the communities we serve, and strive daily to provide safe, reliable service to customers.