A geyser is the heaviest energy consumer in your household

Geysers make up for about 40% of your overall electricity bill. By adding a heat-pump you can achieve the same heating of water at round-about 1/3 (or even less) of the energy cost.

Now if you add solar thermal heating on top of a heat-pump, this cost can be driven even further down to under 1/4 of the normal energy costs. It is like using your geyser as a battery to store energy in the form of hot water.