> solar power inverters are not exactly military and high security stuffs

I'm only familiar with the UK grid, but yesterday, the UK generated a peak of about 11GW of electricity from Solar power.

If you can control 10% of that, and turn it all off simultaneously, you will probably kill most of the UK grid for about 24 hours, similar to the breakdown that happened in Spain recently. I imagine that other parts of the world will be similar.