The tables on this page show the output of the large (20 megawatts and higher) generators feeding the Ontario grid, and the environmental price we pay, in CO2 dumped into the air, for each megawatt-hour of the electricity these generators provide.
Table B5, on the upper right, compares Ontario’s grid-electricity CO2 with that of other Canadian and foreign jurisdictions. Bear in mind that the Ontario numbers in that table are from 2010.
For current Ontario CO2 intensity per kilowatt-hour (CIPK), have a look at Tables A1 and A2 in the left sidebar, and for yearly output by month, see the yearly tables below. You’ll notice a big difference between Ontario’s CIPK in 2010 and 2014 (and so far in 2015). Compare those with the CIPKs of the various jurisdictions in table B5. Any idea why there is such a big difference? (Hint: Germany started phasing out nuclear, which emits zero CO2, in 2011. Ontario was busy adding nuclear during that period.