Here is an installation of an unvented hot water cylinder. We install these to provides high-pressure hot water to taps and showers. And you don't need a cold water storage tank.
It is space saving and will give you consistent hot ware flow across your property. You can be using hot water feeds across your home without losing the heat or the pressure. So if you are lucky enough to have two showers in the house, there is no restriction on waiting for your shower time!