Link? I never heard of this and I'm very interested

You might check the rates on Tibber as well. A lot of companies that offer a "free" usage period tend to just move the cost around. If you're comfortable taking the risks associated with a wholesale supplier, then you can likely save a ton of money without even changing your consumption habits.

During this past month with the heatwave, my electricity bill was only about €50 despite running airco all day most days. I have 6 solar panels on my roof for reference (was 3k installed I believe). If I was willing to turn off the A/C at night, I could have easily cut the bill in half since most of the billed usage was between 18-21:00.

https://www.budgetthuis.nl/energie/gratis-stroom