In this paper we investigate the design rules of electrides using a high-throughput approach. We find that the plus one valence rule is a surprisingly simple yet powerful motif in finding and designing new electrides by applying probable valence charge to all stable materials in the Materials Project database. In doing so, we identify 51 candidates as potential new electrides that were not reported previously and are able to use these to further comment on the relevance of the remaining two design principles. Overall, we conclude that electrides encompass a richer and broader swathe of chemistries than was thought possible until now, while confirming the effectiveness of at least two of the extant design rules.