Okay! I was only wondering how it was working as expected earlier, as I didn’t change anything for several weeks, and the issues started happenning only in the last couple of days. But thanks to you, I have changed all my powercalc sensors to “left” and everything seems fime.
There were recently a change, where a periodically update was removed because of indifferences with HA own periodically updates. So it might be related to this, so now a triangle was calculated from far in the past and starting at 0 to the as is at some point in time with on-value. And before it was drawn from a somehow nearer in the past to the as is with on value. Both ways would be wrong for such on off sensors, the one more then the other.
That seems a plausible explanation for the observations! Thanks again!