Pörssisähkö.live
Finnish electricity is commonly billed on the spot market in 15-minute windows, so households end up timing laundry, sauna, and EV charging around whatever the price is doing. Pörssisähkö.live shows the price right now, the full curve for today and tomorrow, and the cheapest continuous stretches for running something — in Finnish, free, no signup.
The existing sites for this are cluttered and slow, so the build is built around speed: every price is rendered server-side into the HTML and the page ships almost no JavaScript. I built and shipped it solo — concept, code, and deployment.
Under the hood it pulls from the EU's ENTSO-E Transparency Platform, with an automatic fallback to Estonia's grid operator for when it times out (which happens more often than you'd expect), and it's correct through daylight saving time's 23- and 25-hour days. The data layer is config-driven by bidding zone, so the rest of the Nordics and the Baltics are mostly a config entry away.