Geographically distributed computational infrastructures, based on the grid paradigm, are increasingly coming out of the research sphere where they originated, candidating themselves as a low-effort business solution for accessing and using vaste computating infrastructures, much larger than those small-medium enterprises can usually afford building ”in house”. In such scenario, accounting and billing systems play a key role, as any business model cannot opt out of instruments showing how many resources have been used in a given period of time and by whom. For this reason, several accounting systems have been developed in the last years, for various grid middleware. Although each of them has its own features, they are generally targeted for large-size infrastructures, because of the comprehensive range of results available and the vast effort to implement and deploy them. However, sometimes different needs arise, especially for smaller sites participating to large distributed infrastructures. Gustav aims to fulfill some of these requirements in a simple and reliable way, and could be considered as an alternative approach to CPU accounting for grid sites.