7-9pm: decreased demand or political posturing?

I was curious about the extent to which the relatively recent change in the 7-9pm period (in the time-of-use environment) from ‘mid-peak’ to ‘off-peak’ was justified.  In other words, to what extent did demand drop during this time, or, alternatively, to what extent was it a departure from efforts to represent some kind of ‘real-time market’ in electricity in the name of ‘good politics’?

To investigate further, I pulled out some recent data – namely, for the eight weeks from 2 July to 26 August 2011, I collected, from the IESO website, the non-holiday weekdays (all 39 of them), and examined average ‘spot market price’ (Hourly Ontario Energy Price) and average Ontario demand.  These results are presented in the two graphs below, with the two hours of interest (7-9pm, which are ‘hours ending 8pm and 9pm in IESO-speak) circled in each.

Visual observation of these graphs suggest that while there is some ‘drop-off’ from the late afternoon peaks, the values still seem ‘moderate’, suggesting that ‘mid-peak’ may well have been right.  To look at it another way, I took the average values for each of these 24 hours, colour-coded them (red for on-peak, yellow for mid-peak and green for off-peak) and then ranked them from ‘top’ to ‘bottom’.  That graph appears below.  That graph further suggests that the 7-9pm period – at least on the basis of this limited investigation – might more rightly be called a ‘mid-peak period’.