Aim of the study:
The objective of this study is to compare two methods for estimating the daily total solar radiation (SR) based on measurements from neighboring meteorological stations, taking into account the mutual distance between the stations.

Material and methods:
Using data from five stations located in lowland areas of Poland, two methods for estimating daily total solar radiation at any given station were proposed, both utilizing measurements from a neighboring station. The first method relies on the direct use of radiation measurement data from the neighboring station, while the second method employs an estimation formula derived from daily temperature and precipitation values recorded at that station. The analysis of estimation errors as a function of distance enabled identification of critical distances for the application of each method.

Results and conclusions:
The results indicate that estimating SR using direct radiation measurements is recommended for locations up to approximately 100 km from the reference station. Beyond this distance, the method based on meteorological variables and the derived formula for the nearest station is more advantageous. The recommended critical distances vary seasonally and range between 50 and 150 km. Stations selected for analysis were situated at similar latitudes.