Cold thermal storage is primarily used for demand management on electricity grids due to air conditioner use. The CO, hydrate has been widely studied as a cold storage medium for its proper phase equilibrium temperature range and large latent heat. This study presents experimental work on the phase equilibrium behavior of the CO2-hydrate under applicable pressures (<10 bar) for the potential to use in air conditioning systems. The formation of hydrate was aided by tetra-n-butylphosphonium bromide (TBPB) at mass fractions of 10, 20, 30, and 37 wt % to lower the required pressure. Instead of using complex calorimeters, the enthalpy of the CO2-TBPB hydrate was measured using a modified T-history method in a self-fabricated pressure tube. Through this test, the enthalpy of the CO2-TBPB hydrate was found to be much higher than for other normally used phase change materials. However, the hydrate formation was also manifested in a large degree of supercooling and a long induction delay. To reduce them, secondary promoters, namely, sodium dodecyl sulfate and TiO2 nanoparticles, were used. Meanwhile, the effect of feed pressure, heat-transfer fluid temperature, promoter concentration, and the memory effect on CO2-TBPB hydrate formation was investigated. This study provides suggestions for effective and efficient operation of CO2-TBPB hydrate-based cold storage air conditioning systems.