That's the most energy efficient consumer community freezer option, definitely. If you want both a freezer and refrigerator, then I'm not sure because we would need to account for the additional production and redundant cooling systems vs. energy savings from the better cool air retaining abilities of both (and whether they're top opening vs side opening). I would suspect that your standard freezer-top combo is probably the best if it has enough space for your needs and then adding a top-open chest freezer if you need more freezer space.