Might be worth looking at a marine application. Boats have small (25L) calorifiers fully insulated which heat up off the cooling water from the engine. These heat up very quickly (20 mins or so). They also have mains powered immersion heaters for a shore based electrical supply.
One drawback however - as with all things marine they are not cheap.
Do you need very hot water or just warm water. If warm then some kind of blending valve may be the way to go to give a supply temp of, say, 35deg C. That way you would not use the whole hot water capacity on one house.
One drawback however - as with all things marine they are not cheap.
Do you need very hot water or just warm water. If warm then some kind of blending valve may be the way to go to give a supply temp of, say, 35deg C. That way you would not use the whole hot water capacity on one house.
