The thermal reliability of Al-Si eutectic alloy as phase change materials (PCMs) was investigated through vacuum thermal cycling 250, 500, 750, and 1000 times going through the solid-liquid phase change. The changes in thermal properties of Al-Si eutectic alloy, including melting point, latent heat, specific heat, thermal diffusivity and thermal conductivity, were investigated using differential scanning calorimetric (DSC) and laser flash apparatus. The results revealed that, with increasing the number of cycles, the melting point and latent heat of fusion of the Al-Si eutectic alloy showed almost no changes. Moreover, the thermal conductivity showed an outstanding stability after 1000 thermal cycles. Therefore, it is concluded that the thermal reliability of Al-Si eutectic alloy is more than adequate for long-term performance as a phase change material for thermal energy storage (TES) applications. (C) 2017 Elsevier Ltd. All rights reserved.