The rising costs of energy for hot water demand are a urgent concern for consumers relying on grid-connected heating technology in buildings, particularly in developing nations with energy shortage. The reliance on grid-connected water heating technologies such as electric heaters and heat pumps poses significant environmental and energy issues Several demand response measures, including grid load scheduling and shedding, have been implemented to reduce energy consumption. However, these techniques have not produced sustainable solution to rising heating demand in buildings. As a result, integrating renewable and multi-source energy systems offers a promising alternative option for decreasing energy use and costs in residential buildings. This paper proposes an optimal operation of heat water heaters in an integrated solar thermal-grid-energy systems under time-of-use pricing strategy for residential buildings. The main focus of this study is to minimize electricity costs through optimal control strategy. The impact assessment of optimal control strategy on hybrid model was also assessed in terms of cost savings when compared to the baseline heat pump water heaters. The optimal control (OC) strategy had an achievable energy savings of 61.14% and a cost savings of 70.83%. Therefore, better utilization of the propose hybrid system with OC strategy saves 45. 4% more energy than heap pump water heaters (HPWHs).