Prices

Each statistic covers the trailing twelve months ending with the last complete operating day, or as much of them as the history held here allows; a figure resting on under 90% of the intervals its window should hold is not shown.

• Averages are the plain mean of every interval in the window (every interval of a market has the same length), not weighted by load. The window is the trailing twelve months to the last complete operating day; where less history is held, the window column says so and a short window is marked in its cell.
• Day-ahead and real-time are each market's own: ERCOT's real-time prices are 15-minute settlement point prices, SPP's 5-minute (read once an hour), CAISO's the 15-minute pre-dispatch market (RTPD), NYISO's the hourly integrated price, and Great Britain's the half-hourly system (imbalance) price, which has no day-ahead counterpart.
• Basis is the location's price minus its market's reference hub's, interval by interval, averaged; NYISO has no reference hub here, so it has no basis.
• Negative-price hours are the share of the window's intervals priced below zero.
• Daily spread is each complete day's four highest hourly prices less its four lowest (real-time prices averaged to the hour first), averaged over the days.
• Sorting: the last-30-days, basis, negative and spread columns show the day-ahead figure where a market has one and the real-time one for Great Britain, and sort on what they show. Pound prices sort after dollar prices, never between them.