Cask Loader, an EPRI software system is a relational database program that facilitates the automated selection of candidate spent fuel assemblies for placement into dry cask storage canisters from spent fuel pools. Cask Loader allows users to compute the decay heat values for an extended burnup range using a modified regulatory guidance approach. Due to increased efficiency in operation, the number of assemblies with higher burnups increased exponentially within the past two decades. The NRC Regulatory Guide 3.54, published in 1999, set applicability limits for burnup that are below the current operational experience. Subsequently, within the past decade, the need for extending the burnup ranges significantly increased. Only two measurement points are available for extended burnup range. Analyses were performed for these two points and extended by including additional typical and hypothetical PWR and BWR assemblies. For this study, decay heat values were computed using Cask Loader and ORIGEN and were then compared against each other. The computational results showed that compared to ORIGEN, Cask Loader overestimates the decay heat values without any exception and therefore can be considered conservative in its estimation of decay heat values for high burnup range. In this paper, the comparative decay heat values are presented.