Why day-ahead power prices swing so much
Day-ahead electricity prices are set the day before delivery, when generators and buyers submit bids for each hour. The clearing price is where supply meets demand.
What drives the swings
- Demand profile — mornings and evenings pull prices up; nights fall.
- Renewable output — abundant wind or solar pushes the merit order down and can send prices toward zero, or even negative.
- Fuel and carbon costs — gas and CO2 allowance prices set the marginal cost of the most expensive running plant.
When a cold, windless evening lines up with low renewable output, the most expensive peaking plants set the price and the market clears far higher than average.
Why it matters
Understanding the day-ahead curve helps consumers shift flexible load to cheaper hours and helps traders anticipate where the market is headed.