Solar radiation data are essential for many applications, and in particular for solar energy systems. Because ground-based measurements of solar radiation are usually scarce, several methods have been proposed to estimate the solar radiation incoming on a horizontal surface at ground level from satellite imagery. These satellite-based estimations can be used as such, or combined with ground-based measurements. Because the satellite data sets differ in spatial and temporal resolution, this study evaluates the sensitivity of the satellite-derived daily surface solar irradiation to the underlying space and time resolution. More precisely, three surface solar radiation data sets retrieved from the Meteosat Second Generation (MSG) satellites are compared against ground-based measurements. Additionally, the benefit of merging information from the ground-based measurements with satellite data is explored. The study finds that the accuracy of daily surface solar irradiation estimates increases by up to 10% by doubling the temporal resolution of the MSG data, while it is largely insensitive to spatial resolution. This suggests that future geostationary satellite missions might primarily improve temporal rather than spatial resolution.