The 3TIER dataset is at higher spatial resolution and uses more satellite images to estimate hourly values of irradiance. This results in a bias that is similar to NREL dataset, but with a RMSE (Root Mean Squared Error) that is appreciably smaller. The smaller RMSE implies that our dataset is more useful as a time-series of values. In other words, our estimates of irradiance are closer to actual observed values than the NREL estimates on an hour-by-hour basis.