I'm sorry, I try to be clear in my writing. I did say "my electricity company emailed me" which was supposed to indicate that this was specific to my local area

I'm sorry, I try to be clear in my writing. I did say "my electricity company emailed me" which was supposed to indicate that this was specific to my local area. London, where I live, has about 9 million people. So I suppose it also applied to them as well. And, I also pointed to a chart of the UK's energy mix. That was supposed to indicate that my blog post was about the UK. As others have pointed out, these <= £0 prices happen fairly frequently.