I use an Efergy meter to monitor my house energy usage, as well as my geyser energy usage.

Here is what the usage was for a  certain day (4 August):

The geyser (in light green), switches on periodically to maintain temperature. It essentially goes from 0W to 3kW when doing this, as is expected.

On 6 August we had a power failure due to stolen copper, and I stayed at home that day to put the lights on my inverter (no solar, just battery backup). During this process, I did some new wiring in the main DB, but didn't touch the geysers wiring at all. Yet since then, this is what I'm seeing:

As you can see, the geyser is now going to some intermediate value between 0W and 3kW. 

What can be the cause of this?

Wierd. What happens when a geyser element starts to give up the ghost?

I think that's it, the sampling rate is much lower in the second graph.

1 hour ago, calypso said:

To me it looks like the Efergy is just picking up far fewer data points which is making the element time seem longer then what they are. 

That geyser is poorly insulated, its having to reheat far too often. 

 

44 minutes ago, DeepBass9 said:

I think that's it, the sampling rate is much lower in the second graph.

The transmitters only have 3 settings, namely 6s, 12s and 18s.

As far as I can see, there is nowhere else to adjust the sampling frequency.