How it works
Intraday trading opens after the day-ahead results are published and runs until shortly before each delivery period. It comes in two forms. Continuous trading works like a stock exchange order book. A buy order matches any sell order at an equal or lower price as soon as it arrives, and each deal has its own price. Intraday auctions collect orders for a set period and clear them all at one price, like a smaller day-ahead auction.
Products are usually hourly, half-hourly or quarter-hourly blocks, traded in MW. Gate closure for each product sits a fixed time before delivery, often between five minutes and an hour. Traders use the window to adjust positions as wind and solar forecasts are updated through the day, as plants trip or return, and as load departs from expectation. Liquidity is thinner than in the day-ahead market, so prices can move sharply as delivery approaches.
Why it matters
Wind and solar forecasts improve markedly in the hours before delivery. The intraday market is where an IPP turns a better forecast into a smaller imbalance bill. For batteries and flexible plants it adds trading opportunities, because intraday prices often swing further than day-ahead ones. A revenue model that leaves out intraday trading can understate what flexible assets earn and overstate what forecast errors cost.
A worked example
A solar IPP sold 80 MWh day-ahead for the 13:00 hour at $30/MWh. At 10:00 a new cloud forecast cuts its expected output to 65 MWh. It buys the missing 15 MWh in continuous intraday trading at $38/MWh, costing 15 × $38 = $570. Left to settle at an imbalance price of $90/MWh, the same shortfall would have cost 15 × $90 = $1,350. The intraday trade saves $1,350 − $570 = $780.
Illustrative figures.
Across markets
Europe's intraday market is deep and cross-border. A shared continuous platform links national order books, and pan-European intraday auctions add points of single-price clearing. India's exchanges offer intraday and day-ahead contingency contracts traded continuously, alongside the half-hourly real-time market. In the US, exchange-based intraday trading is rare. The ISO's real-time market fills that role, and bilateral trades handle the rest.