Stats below obtained from Tuya local / Geyserwise integration in home assistant.

Needles to say the poor heating performance of the indoor geyser is irritating me, and it may find itself replaced in the near future.

Also interesting is how the blanket makes little to no difference in cooling performance.

Does anybody have ideas for the heating performance difference?

R.

Edited August 18, 2025Aug 18 by regbes
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to heat water from 30 degrees to 55 degrees with a 2.6kw element that is submerged (100% efficiency) will take 1H40 minutes.

to do the same with a 2.75kw element will take 1H35 minutes.

to heat water from 35 degrees to 55 degrees in 30 minutes will require a 8.7kW element

your tuya/geyserwise system is not accurate.

2 hours ago, stefan44 said:

to heat water from 30 degrees to 55 degrees with a 2.6kw element that is submerged (100% efficiency) will take 1H40 minutes.

to do the same with a 2.75kw element will take 1H35 minutes.

to heat water from 35 degrees to 55 degrees in 30 minutes will require a 8.7kW element

your tuya/geyserwise system is not accurate.

Just to add some info. With a vertical geyser the thermostat/element is at the bottom of the tank. It will switch off with a lot more water at a much lower temp than the horizontal one which is in the middle of the geyser..

I do agree with @stefan44 with the times if the whole geyser was at the same temp. The contents temp will be made up of layers.

Only if water is circulated will you have the whole geyser at a certain temp like with a heat pump.

Google stratification.

29 minutes ago, Scorp007 said:

Just to add some info. With a vertical geyser the thermostat/element is at the bottom of the tank. It will switch off with a lot more water at a much lower temp than the horizontal one which is in the middle of the geyser..

heat rises, but you suggest otherwise here....

30 minutes ago, Kalahari Meerkat said:

heat rises, but you suggest otherwise here....

Heat does rise over time but the element is at the bottom where the cold water enters and that gets heated and takes long to reach the hot outlet at the top. The thermostat reacts to the water that gets heated around the element.

6 hours ago, regbes said:

Also interesting is how the blanket makes little to no difference in cooling performance.

Of course, you don't just lose heat from the geyser itself (that might be improved by insulation with a blanket), but a lot of heat is also lost through radiance from the pipes, all the way from the geyser to the hot water taps. If you have not already done so, you should apply lapping around the pipes, preferably up to the point where they enter the walls.

Also, as mentioned by @Scorp007 , you should really keep the water circulated before any accurate conclusions can be made regarding the efficiency of the two geysers.

As @stefan44 stated, the power consumption vs water temperature don't make sense - this is quite likely because of localised heating, with both the temperature sensor and thermostat placed close to the heating element. Again, circulation of the water through the geyser would be the only way to really get to an accurate evaluation.

15 hours ago, HennieL said:

but a lot of heat is also lost through radiance from the pipes, all the way from the geyser to the hot water taps. If you have not already done so, you should apply lapping around the pipes, preferably up to the point where they enter the walls.

#canConfirm. When we had our ceilings insulated, the guys who did it also wrapped the geyser, and all the hot water pipes to the point where they entered the walls. We now have hot water for hours after the actual heating has taken place.