Mechanical cooling is responsible for a significant fraction of the energy consumption of data centers (DCs). Free cooling systems take advantage of ambient conditions to reduce the need for compressor-based cooling. This study utilizes thermodynamic models of major free cooling systems such as the direct air-side economizer (ASE), indirect air-side economizer (IASE), indirect evaporative cooler (IEC), and indirect water-side economizer (WSE) integrated with the existing cooling infrastructure of a typical 1 MW IT load DC. Proposed models utilize hourly weather data of various cities in Turkey to compute annual energy consumption and cost-saving potentials of each free cooling method with respect to the baseline DC with both open aisle (OA) and enclosed aisle (EA). Results confirm the energy-saving potential by IEC leading to less than 10% of annual chiller hours across Turkey and less than 1% in half of the ten cities studied, especially in EA DCs. However, despite greater energy-saving potential, IEC has more extended payback periods of 1.5 to 3.7 years due to the high capital investment compared with those of ASE and WSE with less than 1.4 years.