How do plug-in photovoltaic cells work with three-phase current electricity meters?

Question

First off: I'm German, and while I have a bit of knowledge of electrical distribution systems, I am not too experienced with English terminology for the technical terms. So please bear with me. Also: I'm talking about a 380 V / 230 V TN-C-S distribution system which three phases into the house and electricity meter and a single phase to each outlet.

There are small photovoltaic cells on the market currently which deliver around 400 to 800 W peak and are intended to be plugged into a (modified / strengthened) 230 V outlet. The energy is, ideally, directly consumed within the same household.

However, I was wondering how the electricity meter sees this. I have a bi-directionally-aware electronic meter that can measure current flowing in both directions independently (which is required for tax purposes in Germany).

Say I connect the solar cells to L1, producing 800 W, and have my washing machine on L2, drawing 2 kW. This creates a "Schieflast" (asymmetric / unbalanced load) on the net. Does my meter count the 1200 W net power I pull from the grid (how?) or something else? How does the balancing of currents work in this scenario?

Answer 1

What the meter records depends on its programming.
A neutrally programmed / technically correct meter will record the difference of 1200 W.

An administration may decide to do things differently.

Answer 2

That's a good question but difficult to answer without details of the meter.

If you are lucky the meter would total (power import - power export) and charge you for the difference.

If the meter is "smarter" it will register each phase individually, charge you for the import at normal electricity rates and give you credit for the export at (usually much lower) generation rate.

As I think you suspect, the lowest energy bill will be given in the first case. Offsetting energy import always gives the best result.