It is the norm to have twin elements in geysers over in Ireland.
The geysers usually are vertically mounted in the house’s airing cupboard, and the elements are physically two different lengths. A switch is next to the geyser with the option of “sink” or “bath”.
One element is typically around 2kW and the other about 3kW.
So you could have 2, 3 or 5kW selections if you really wanted.