Disclaimer: This comment, and my other one, are the first time I've actually thought about this. The amount of tank heat loss would depend on the temperature d

Disclaimer: This comment, and my other one, are the first time I've actually thought about this. The amount of tank heat loss would depend on the temperature difference between the water & the environment; a tank that's kept hot will lose more heat than one that's warm. So I think it's a marginal gain to let it cool, but only marginal. And: the better-insulated your tank & plumbing are, the less you gain.