What was the source of that energy loss? No idea.

I tried to figure it out myself first, then I had two electricians independently checking it.

And their conclusion was that they didn’t know, and that the 5% was sort of normal. I even had my electricity meter recalibrated by the grid company. I was afraid somone was taping, but no… It still could’ve been the my electricity meter ( which was like only 10 yo), so to be" safe", I have now a newer smart electricicity meter.