CenterPoint Energy Inc. executives have added $1.2 billion to the utility’s investment plan because of strong demand from customers in its Houston service area and work on resiliency work in the city. Two-thirds of the increase to CenterPoint’s previous $65.5 billion plan is powered by large-load customers. The remaining $400 million of the capex increase reflect a new estimate for spending as part of investments focused on downtown Houston. While the new $1.2 billion is officially part of CenterPoint’s 10-year capital plan, the company will spend that amount over the next five years. Doing so, Wells said, will lift the annual growth rate of Houston Electric’s rate base to 18% over the next three years.