alt Hacker News> if you're producing so much excess that selling it back would actually cost you money, wouldn't this be a pretty good case for something akin to those Tesla Powerwalls?
Yes, I mentioned that in my comment. They are quite an investment, and they're impractical to place in many houses. So it's not always an option. I personally have the space. But there's some ongoing projects that make it impossible for me to currently install them.
Again, I don't know the laws in other countries, but in the US, it's generally relatively cheap to build your own powerwall with used electric car batteries. Total investment would be less than ~$2000 (United States dollars) though you would need to check your local laws to see if you're allowed to install it yourself or need a licensed electrician. Might be worth looking into.