How it works
Before each delivery day, every scheduled party tells the grid operator what it plans to inject or draw in each block, in MW. A generator's schedule reflects its forecast, its contracts and its market trades. A buyer's schedule reflects its expected load and the supply it has arranged. The operator checks that the schedules balance and that the network can carry the resulting flows.
Schedules can usually be revised up to a set time before each block, often an hour or a few blocks ahead. Revisions follow updated forecasts, plant outages or new trades. Once the gate passes, the schedule for that block is fixed. After delivery, the metered energy for each block is compared with the final schedule. Any gap is settled as a deviation or imbalance, usually at a worse price than the market offered. Renewable plants may also declare their available capacity separately, which matters when they are curtailed and claim compensation.
Why it matters
The schedule is the commitment that every deviation charge is measured against. For a wind or solar IPP, scheduling is mostly a forecasting problem, and the quality of each revision decides how much revenue is lost to penalties. For a buyer, a poor load schedule means paying imbalance rates for energy that could have been bought more cheaply ahead. Revenue models that assume perfect schedules overstate what a project will earn.
A worked example
A 50 MW solar plant declares 30 MW for the 15:00–15:15 block, or 30 × 0.25 = 7.5 MWh. Cloud cuts actual output to 24 MW, or 6 MWh. The 1.5 MWh shortfall is settled at a deviation price of $80/MWh, costing 1.5 × $80 = $120. Had the plant revised its schedule to 25 MW at the last allowed gate, the shortfall would have been 6.25 − 6 = 0.25 MWh, costing $20.
Illustrative figures.
Across markets
In India, generators and buyers submit day-ahead schedules to their load despatch centre and can revise them during the day, with wind and solar allowed frequent revisions. In Europe, schedules are submitted through a balance responsible party, and Great Britain calls them physical notifications. In US nodal markets, the day-ahead award acts as the schedule, and the real-time market settles departures from it at the nodal price.