Geyser tested fine. All results good. No problem with element or thermostat. Tempeperature callibration correct as indicated on the thermostat.
Problem is that after connecting the data logger(out of interest sake) I picked up that the thermostat was kicking in too much. There were "blisters" visible on the geyser. Turns out that these "blisters", which have been there for years, were actually tell-tale signs that the geyser actually leaked into the insulation. The insulation had over the years become saturated with water and that was absorbing the heat of the water. This led to the thermostat having to kick in all the time. I disconnected the geyser and have experienced since then a drop in monthly electricity consumption of between R800.00 to R1 000.00 per month. The geyser was switching on too often albeit at the correct temperature.