From 2010 to 2020, energy consumption in the Middle East increased by 24.2%. Because this region, in step with other regions of the world, has suffered from the phenomenon of global warming, but at a higher rate. At the same time, the share of renewable energy in this period has not changed much. We examined PCM effectiveness for four hot regions along with four cold regions. The results showed that the effect of PCM on heat exchange in winter and summer can be quite the opposite. Therefore, the appropriate PCM was selected based on annual analysis. Annual calculations show that for hot regions, the maximum energy-saving was obtained for PCM-24. In these zones, the maximum energy saving was within the range of 19–30 kWh per square meter of building floor. For cold climates, PCM-22 had the best performance. In these regions, the saving energy was in the range of 30–55 kWh/m2. It was found that if PCM is not selected properly, it can increase the building energy demand. PCM thickness intensifies the positive or negative effects of PCM. If PCM reduces heat exchange (positive effect), it intensifies as the PCM thickness increases. Conversely, if PCM increases energy consumption, increasing PCM thickness will make it worse.