And permits and other hoops to jump through.
In the Netherlands, f you have an old-fashioned meter (with a rotating disc), you don't have to do anything at all. Just watch the disc spin backwards and the displayed value decrease :-)
Here, if I needed a second meter and its charge to be read, I would loose money!
If you have a newer, digital meter it gets a bit more complicated. The energy companies have to read the second meter and pay you the complete value of each kWH (production, tax, transport, etc.). There is a special law for it. There are some problems here and there with the energy companies dragging their feet, but by and large the system works.