Some context based on recent history (EU/Finland perspective):

- On average the market electricity contracts are cheaper than flat-rate contracts

- Day-to-day (and hour-to-hour) variation can be huge; yesterday evening it was 32 c/kWh, tomorrow it'll be about 2-3 c/kWh for most of the day.

- You know the day-ahead prices around noon (UTC), so you can plan ahead.

- EU has a wholesale electricity price cap; not sure what's the current value but it was 500 c/kWh a while ago. Plus taxes, probably.