What a high or low reading means
Electricity demand is the load the grid must serve, and its seasonal band captures the climate pattern: summer cooling and winter heating peaks. A reading above the band means weather or economic activity is pulling load beyond the historical pattern. The configuration that tightens wholesale power prices and, for a grid near capacity, raises outage risk. The seven-day average smooths the daily weekend/weekday sawtooth; heat waves show up as the band is breached and stay visible for the week.