Among the oldest public utilities in the Commonwealth, T. W. Phillips has provided reliable service to customers in southwestern Pennsylvania since 1896.  Its history extends to the earliest days of the natural gas industry in the United States. As an integrated gas utility, T. W. Phillips is engaged in the purchase, transmission, and distribution of natural gas to the public in various communities in Allegheny, Armstrong, Beaver, Butler, Cambria, Clarion, Clearfield, Indiana, Jefferson, and Westmoreland Counties, Pennsylvania.

As of the end of 2008, T. W. Phillips served approximately 62,800 customers, of which 58,350 were residential, 4,400 were small commercial and industrial, 20 were large industrial, and 5 were other natural gas utilities.