Q1: How much does an off-grid BTS hybrid system cost? Typically $20,000–$60,000 per site, depending on configuration and location. Q2: What are the savings compared to diesel-only sites? Up to 40% lower OPEX through reduced fuel and maintenance. The second design is a hybrid system including a wind turbine, PV modules, diesel generator, and battery, and finally, a hybrid syste that contains a wind turbine, diesel generator, and battery as the third design. Battery choice: Lithium iron phosphate (LFP). Hybrid Renewable Energy Systems (HRESs) are a practical solution for providing reliable, low-carbon electricity to off-grid and remote communities. It applies a borehole thermal energy storage to store solar energy in non-heating seasons, and uses stored energy for part of total heating demand in a residential neighbourhood in heating seasons.