Green Energy

The main issue is that the grid was designed to go from a few large providers to a lot of small consumers. The equipment was designed with this, one way flow design, in mind.

Think of it a little like waterfalls. It's easy to get water from a single source at the top of a hill, down to many ponds at the bottom. It's far harder to get water from 1 pond to another.

In practice, this means that load balancing can be problematic. 1 area might have a glut of power. This sounds good, but it's actually not. Without something drawing power, the voltage (and frequency) can climb. This can cause power spikes etc. This is why the wholesale price can sometimes go negative. The power plants are pushing too much power in, and can't shut down fast enough. They actually pay companies to draw power, to keep the grid stable.

Conversely, other areas might have a sudden drop in capability. With a centralised grid, they can predict and balance this. With a highly localised grid, it can destabilise before they can correct. This will cause either a blackout, or a brownout event. Neither are good.

Basically, the grid needs to be adjusted to move power in ways it was never expected to have to move it. It will also need to react to faster changing supply or demand. Putting the equipment and cabling in to do this is slow and expensive.