I was checking a monthly report I produce and noticed the 12-month total of “Ontario Demand” is currently almost exactly the same level it was 5 years ago.

So I looked at data for both, summarized by hour of day:

In IESO jargon, “Ontario Demand” refers to generation on the IESO transmission grid, so embedded generators impact reporting by reducing demand. The IESO currently states there is 1503 MW of embedded solar generation, and 425 MW of wind capacity (both figures are from the end of 2014).



The chart shows demand isn’t really flat at all - it’s up about 375 megawatts (MW) in the early morning hours, and the growth in embedded wind should make that, in reality, closer to 500 MW. The downward bump, bottoming at hour 12 (the IESO is always on Eastern Standard Time), is probably due to embedded solar.

Close followers of Ontario’s ridiculous electricity exploits might recognize daily peak demand being pushed further back in the day - into the off-peak hours that start at 7 pm.

May 2015 had a similar “Ontario Demand” total to May 2009, so I also charted just May:

Notable here is that the average hourly peak “Ontario Demand” was, on average, in hour 21 in 2015, far from the hour 12 peak in 2009 (that’s 9-10pm during daylight savings time) . I suspect the difference between the years drops, after people drop off to bed, due to supply curtailment being increasingly necessary, with the daytime drop again reflecting the inverse of embedded solar’s generation.





Summary data, by year and month, is here