This paper presents the results of the experimental tests of the cooling performance of a 3.5-kW condensing modified air conditioner (referred to as the CM-AC) by using the ground as a heat sink of a condensing unit. In the tests, not only the cooling capacity of the CM-AC with an optimal length of a condensing coil but also the life expectancy of this copper coil buried underground at 1 m depth have been investigated. The lengths of copper coils fabricated and used as condensing units of the CM-AC were set at 67, 50, 40 and 30 m whereas that of a 3.5-kW conventional split-type air conditioner (referred to as the C-AC) was about 22 m. R-134a was used as the refrigerant of both types of air conditioners. The results have shown that the ground has the potential to absorb the heat rejected from a condenser of the CM-AC. The coefficient of performance (COP) of the C-AC was about 2.5 whereas those of the CM-AC were found to be higher values except the case of 30-m-long condensing coil. It was found that the COPs of the CM-AC with condensing coils of 67, 50 and 40 m long were about 6.9, 5.5 and 3.3 respectively while that of 30-m-long one was about 2.1. The electrical consumptions of the CM-AC were found lower than that of the C-AC, on average, 11-15%. In addition, the ground temperatures near the buried copper coil had been increased insignificantly during the tests (< 1.5°C). Moreover, it was found that the underground condensing coil of the CM-AC can be used as a condenser without any damages for more than 5 years.