> But seriously, just adding more power or just shed load is not easy.

It’s all a question of scale, you need coordination to handle the macro level balancing of power. Making sure there’s enough power stations running to keep the lights on, and that the grid is roughly balanced. But that level of balancing is planned hours to days in advanced, because power stations take hours to days to spool up depending on the tech. So it’s a system incapable of responding to moment-by-moment changes.

For handling instantaneous fluctuation, the first defence the the rotational inertia of all the generators in every power station. These things have tons of spinning mass, and are the reason grid frequency fluctuates with power draw, pull more power than provided, and the grid makes up for it by stealing stored spinning energy in the generators. Then speed governors on the generators notice the slow down and provide more steam/gas/coal whatever to speed the generator back up. Both covering the stolen inertial energy and bumping total grid input.

For larger fluctuations that can’t be covered by rotational mass and modulating power station output, you’ll have a variety of fast response loads and supplies. Energy consumers that have agreements to modulate their usage or production in response to frequency fluctuations, and who get paid for providing the service. Some examples include steel and aluminium smelters. They can shutdown temporarily to shed load, and just rely on thermal mass to prevent their equips freezing. Water tower pumps, you’ll have plenty of stored water, pumps for canals, fridges and freezers can turn their compressors off, so can AC units, and even data centres that will swap to their backup generators and take their load off the grid.

Now all of the above loads heading only works for a limited amount of time, all of those consumers can only reduce their load for so much time. So you also have power producers, people who have diesel generators sitting around that can be turned on and connected to the grid, rapid response power stations that can cold start in 15-20mins etc. All of these will be started by a drop in frequency, and expected to pickup the load without any central coordination.

Between the fast response load shedding and fast response producers a grid can handle a substantial amount of production variation without any central coordination. In normal operations you’ll only be relying on fast response load shedding of non-critical loads like water pumps, and cascading to more drastic load shedding and power production if the grid can’t recover quickly by upping production at major producers (who won’t be running a 100% under normal conditions).

> Decentralized production absolutely can be enough to max out power lines.

> <snip>

> Here in Belgium the grid is such a pile of rubbish that instead of trying to adapt to decentralized production, we're now actively going to punish people for using power during peak hours.

Yes and no. Normally the behaviour you describe isn’t caused because the infrastructure can’t handle the production (after all peak distributed production is extremely unlikely to ever be higher than peak load, you simply can’t fit that many solar panels on a roof). But rather that distribution companies run on the assumption that power only passes in one direction in their network, from grid to consumer. All of their modelling, and more importantly, their financial agreements with the grid and each other depend on this predicate.

As a result their objective is to ensure there is zero supply back to the grid, and that all distributed generation is always consumed within their grid, preferably within the same substation so there are zero backward flows anywhere. This doesn’t mean the equipment couldn’t support reverse flows, it’s just that figuring that out would cost money, and they have no incentive to figure it out. They get paid the same regardless of if they support reverse flows or not, so it’s better to obstruct and get government to pay the costs of checking, than it is to pay for it out of a profit margin.

In short our grids are a lot more capable than the industry generally lets on. But using that capability would require profit making companies to invest in work that will never return a positive ROI (at least under the current model that distribution network operators are paid under). So it doesn’t happen, and network operators prefer to spread FUD, than actually innovate (which would risk their margins).