Not a big project, but just last week finished a visualization of electricity spot prices in Finland. Seems like a potentially difficult winter coming in Europe, using spot priced electricity and optimizing use would make sense. I didn't find a good visualization, so I made my own.
Open source, GitHub link at the bottom of the page. The API used serves a large part of Europe, so you might be able to fork the code and adapt it to another country with fairly minimal work.