This paper presents an experimental study on a single tank thermal energy storage (TES) system integrated with a cooking unit. The tank had a capacity of 45 L of oil. The cooking chamber was embedded in the storage tank, thereby eliminating the use of pumps and connecting pipes between the cooking unit and the storage unit. The system was designed to make good physical contact, circumferential and basally, with the cooking pot, to improve the rate of heat transfer. Experimental tests were performed with oil only and oil–rock pebbles as sensible heat storage materials. The charging unit was connected to the TES unit in such a way that it allowed circulation of oil between them during charging, using the thermosiphon principle. An electric heater rated at 800 W 240 V was inserted into the charging unit to charge the system. The thermal performance of the TES systems was evaluated in terms of the charging temperature, heat retention capacity, energy stored and cooking efficiency, and the overall heat lost coefficient. The results showed that the oil–rock system performed best, with a cooking efficiency of 64.9%, followed by the oil-only TES system, with 60.3%. Further tests on cooking indicated that the system was able to cook beans in 2.25 h and 2.0 h using the oil only and oil–rock pebbles thermal energy storage systems, respectively.