Exhibit 21 Significant Subsidiaries of Centerpoint Energy, Inc. The following subsidiaries are deemed "significant subsidiaries" of CenterPoint Energy, Inc. pursuant to Item 601(b)(21) of Regulation S-K: o Utility Holdings, LLC, a Delaware limited liability company and a direct wholly owned subsidiary of CenterPoint Energy, Inc. o CenterPoint Energy Investment Management, Inc., a Delaware corporation and an indirect wholly owned subsidiary of CenterPoint Energy, Inc. o CenterPoint Energy Resources Corp., a Delaware corporation and an indirect wholly owned subsidiary of CenterPoint Energy, Inc. o CenterPoint Energy Houston Electric, LLC, a Texas limited liability company and an indirect wholly owned subsidiary of CenterPoint Energy, Inc. o Texas Genco Holdings, Inc., a Texas corporation and an indirect wholly owned subsidiary of CenterPoint Energy, Inc. o Texas Genco LP, LLC, a Delaware limited liability company and an indirect wholly owned subsidiary of CenterPoint Energy, Inc. o Texas Genco, LP, a Texas limited partnership and an indirect wholly owned subsidiary of CenterPoint Energy, Inc. (1) Pursuant to Item 601(b)(21) of Regulation S-K, the registrant has omitted the names of subsidiaries which, considered in the aggregate as a single subsidiary, would not constitute a "significant subsidiary" (as defined under Rule 1-02(w) of Regulation S-X) as of December 31, 2002. (2) CenterPoint Energy Resources Corp. also conducts business under the names of its three unincorporated divisions: CenterPoint Energy Arkla, CenterPoint Energy Entex and CenterPoint Energy Minnegasco.