> Power suppliers don't like this because it favors cheaper sources of power that push their more expensive legacy generation out of the market.

Meanwhile a common scam in several EU countries consists in having the power supplier that is either fully state-owned or officially a private company but actually state-ran behind the scenes and... They force you to give back any excess power for free to the grid.

At the same time ofc they pass crazy laws mandating most of the energy generated to be sold for pennies on the dollar to other state ran companies, while then reselling it based on the price of... natural gas. It's quite the wonderful state-ran scam. Some politicians denounced that scam when electricity prices skyrocketted in France etc. a few years ago.

So not only do they steal people's produced energy but they also make sure to resell it at an inflated price, while their little friends in fake privately owned companies are lining up their pockets (the scheme is very probably complete with illegal kickbacks to the politicians).

I know not one but two person who have powering on on-demand... Cryptocurrency mining equipment (for some GPU based ones)! This way they make sure to not give back for free electricity to the state. Sucks but it's what it is. Wouldn't be that way if these people were paid for that excess energy.

They simply don't want to encourage this government ran electricity scam.

Yes, one of the problems of renewables is that they are highly correlated as to when they generate power, so the value of the power they produce (per kWh) is much lower than it would be if they were uncorrelated with each other. Since we have all invested so heavily in renewables, there is generally a huge amount of excess power generated at these peak times that has to be burned. The correct marginal price of those joules that have to be burned is $0.

Providing that power back to the grid for free is about the right price for the power, and if you would like to be the one to burn it instead (because that is what the grid is doing with a lot of that power), I assume you are free to do so.

"They force you to give back any excess power for free to the grid."

If the power being generated is in excess of what the grid is consuming then it is worthless. I've seen people suggest installing bitcoin mining hardware directly inside wind turbines so they can consume excess electricity and make a profit.