Day-ahead trading refers to the process of buying and selling electricity for delivery on the following day, based on forecasted demand, generation availability, and market prices. Conducted in organized electricity markets, such as the European EPEX SPOT or U.S. ISO markets, this type of trading enables market participants to secure positions in advance, manage risk, and ensure system reliability. Day-ahead prices serve as reference points for real-time markets and impact long-term planning and financial hedging.