A novel solar thermal energy storage (TES) system for house heating purposes is modeled in the present study. The solar parabolic collector acts as a heat source to charge the TES using compressed CO2. The thermal energy in terms of sensible heat is stored in mild steel (MS) block wrapped in the thermal insulation material and buried in the ground at a certain depth. The stored energy will be used for house heating in the winter season. A mathematical model is developed to calculate the quantity of stored energy, consumption, and loss from TES along with the optimal storage volume of the block to fulfill the energy demand for house heating. Computational analysis of the 3D model is executed by adopting stipulated boundary conditions. Quantitative and qualitative studies of numerical results have been investigated for two cases: Initial charging and year-round performance. Numerical results revealed that the initial charging of the block takes in 55.2 days with maximum block temperature and stored energy as 324.2 °C and 2604 MJ, respectively. The average exergy efficiency and exergetic effectiveness of TES are observed as 49.9 % and 0.50, respectively. The partial charging of the block continued to compensate the heat losses after initial charging. The year-round performance of TES exhibits the reduction of stored energy by 71.6% at the end of January due to increased heating demand. Meanwhile, during a cyclic year, the average exergy efficiency and exergetic effectiveness of TES are noticed as 56.12 % and 0.76 respectively. The proposed TES has enough potential for year-round house heating since 28.4 % of net stored energy exists with the least block temperature of 106 °C. The rational economic study endorsed the proposed system 42.5% less expensive than the traditional heating methods for 50 years of utilization in addition to mitigating the average CO2 production of 5.655 Tons/year.