Adding 2nd holding tank as pre-heat for incoming water
We're considering buying a cheap electric hot water heater and NOT turning it on. It would just to act as a 60 gallon holding tank for incoming water.
In winter, the water temperature of our incoming line is about 3'C/37'F. We thought if that water could sit overnight (even in an unheated tank), it would gradually come up to room temperature (or thereabouts). The other active hot water tank would draw from this holding tank so it would only need to raise the temperature about half what it usually would.
I know the house will ultimately be heating this unit, but it seems like the house would be an order of magnitude more efficient at raising the temperature than a hot water heater would.
Is there a flaw in this logic?