Here's exactly how it works in my case. Since I installed my PV system a long time ago, the 'old rules' still apply to me. These rules included benefits for early adopters, where the grid acts as a large virtual battery with 80% efficiency (hence the 20% fee). New installations can no longer choose this model. Instead, they must sell their surplus energy at wholesale prices, which are typically very low during peak production periods.

For example, if I have a productive month like September and export 400 kWh to the grid, I can later use that energy (minus the 20% fee, so 320 kWh), and I have up to a year to use it before it expires. This was a great offer because it allows us to build up enough energy to cover weaker months (November to February).

Of course, in the real world, this isn't entirely sustainable, as you can't easily find real energy storage with these characteristics. However, context matters. The energy mix in my country was quite poor at the time, so the grid needed green energy desperately. By offering these perks to early adopters, the grid operators were able to secure that green energy through user investments.