it’s not really a myth, see for yourself with the ugliest link ever: https://www.energystar.gov/productfinder/product/certified-residential-freezers/results?search_text=&sort_by=annual_energy_use_kwh_yr&sort_direction=asc&page_number=0&lastpage=0&search-1=&type_filter=Chest+Freezer&type_filter=Upright+Freezer&is_most_efficient_filter=0&capacity_total_volume_ft3_filter=7+-+13.9&capacity_total_volume_ft3_filter=14+-+21.9&markets_filter=United+States
you’ll notice that by capacity chest freezers are more efficient. There are a lot of factors stacked in their favor though:
- cold air sinks as mentioned above, while not the majority of the thermal mass in a fridge you lose quite a bit every time anyway.
- convection is a lot stronger than people often realize, and upright freezers are more prone to unforced convection, especially because of the aforementioned air loss (replaced by warm air flowinginto and out of)
well you can define when the efficiency is impressive or not to you, now people can go look at the numbers. 20% is pretty substantial, but if you are disappointed it’s not 90% then i dont know what to tell ya