Sulfur hexafluoride (SF6) is commonly used in electrical insulation networks due to its superior dielectric properties. However, it possesses a high Global Warming Potential (GWP) of 22,800 times compared to CO2 (at equal mass over a time span of 100 years) and a high atmospheric lifetime. This alarming metric prompted investigation for substitute gases with minor environmental influences. The overall objective of this research is to evaluate refrigerant R152a as a potential alternative for SF6 in electrical insulation systems. R152a gas has a significantly reduced value of GWP (140) and is a cheap insulation medium as compared to SF6. In this paper, dielectric breakdown testing of R152a and a mixture of CO2 with different concentrations have been tested. The dielectric strength of R152a/CO2 gas shows a saturated growth trend with increasing the gap difference, gas pressure and mixing ratio of R152a. Based on our experimental conditions, R152a/CO2 gas reveals good dielectric properties, and insulation performance can reach up to 96% of SF6. Finally, this work will bring a cost-effective and environment-friendly gaseous insulator for utility companies and power equipment manufacturers.