Source? Probably logic?
Tagging an single row of solar panels dosen't make sense, because it isn't a "generating unit".

A solar generating unit is either

- a single solar cell/solar panel. A solar farm this size consists of ~+250,000 individual panels.  - Mapping every single of those as  a generator might be correct, but is BS for obvious reasons.

- or all panels as one generating unit. (with exceptions) This is how the US EIA Electric Generator inventory handles it (US generation standart), and it is the best option. It dosen't yield absurd results like "this solar farm consists of 5,6k generators" (it consists of 250k generators). Also tags like generator:output:electricity are impossible to tag on those small areas.

TLDR: Mapping 5k ways might look good on the renderer, but dosen't look good on the background of electric generation data. 
(This MP is the solar farm's generating unit > those 5000 areas are the solar farms' generating units, which is wrong)
