Evapotranspiration (ET) is one of the main fluxes in the global water cycle. In this context, we assessed an operational methodology based on the S-SEBI model to accurately estimate energy fluxes over the natural grasslands of Pampa biome. The S-SEBI performance was investigated considering radiation data from both ERA5 reanalysis and tower flux. Comparisons from satellite-based estimates with in situ measurements were performed with and without energy balance closure (EBC). Results indicated that meteorological inputs have low sensitivity on daily ET estimates. In contrast, the instantaneous components are more affected. The impact in the daily ET is lower when in situ data without EBC are considered as ground truth, despite they are less correlated with the remote sensing estimates. These insights are useful to monitor water and energy fluxes on a regional scale and provide the opportunity to capture ET trends over the Brazilian Pampa.