- as I said, they get used only a small number of times per year (often at Christmas). Of course, the real killer for the stored hot water approach arises when (usually at Christmas ) one or two of those around decide to have (generously full) baths!
That reminds me of Christmases a few years ago, when my family all went "up North" to stay with the wife's sister.
She had an oil-fired Aga that did the cooking, and fuelled the CH and hot water.
Baths were forbidden on Christmas Day, otherwise the turkey was still raw at 5pm!