This research paper examined the variation in solar irradiance quantitatively over time by comparing solar irradiance data from domestic Typical Meteorological Year (TMY) records. Solar radiation can produce different TMY records depending on the year of data collection, even for the same region. Therefore, simulation users should take these factors into consideration and select appropriate TMY records based on their specific needs. The results showed that the recently produced TMY records had higher solar irradiance values than those produced in the past. The average annual deviation between different TMY records was 86.1 kWh/m²yr (6.5%). However, a comparison of TMY records from KIRE and SAREK, which have a significant difference in publication date, demonstrated that the deviation increased to an average of 204 kWh/m²yr (14.4%), with a maximum of kWh/m²yr (16.9%). The study also found that the difference in solar irradiance is related to the ratio of direct solar radiation when converting GHI to inclined plane irradiance. The annual cumulative solar irradiance showed significant variations on the southern inclined planes with a high ratio of direct solar radiation, while minimal changes were observed on northern inclined planes with a high ratio of diffusion solar radiation.