As someome mentioned, the thermal mass of water is way higher than air, but also, this is the problem that deep freezers solve! Afaik, deep freezers open from the top meaning the cold air does not flow out when you open it. That saves effeciency on your heat pump.
Another neat thing you can do depending on where you live is set a timer on your deep freeze so it only turns on at night. This benefits you if you get charged electricity depending on the hour of the day, meaning you are charged nore during peak hours. Since the deep freeze has high thermal mass and low energy transfer, it stays cold all day.
As someome mentioned, the thermal mass of water is way higher than air, but also, this is the problem that deep freezers solve! Afaik, deep freezers open from the top meaning the cold air does not flow out when you open it. That saves effeciency on your heat pump.
Another neat thing you can do depending on where you live is set a timer on your deep freeze so it only turns on at night. This benefits you if you get charged electricity depending on the hour of the day, meaning you are charged nore during peak hours. Since the deep freeze has high thermal mass and low energy transfer, it stays cold all day.