The McGuinty Liberals are planning on building four more nuclear reactors at the Darlington site. The total cost will be well in excess of 36 billion dollars. The cost is an estimate, these reactors typically end up costing two to three times that.
If you want a reminder of the cost, look at your hydro bill every month. The debt retirement cost is in large part the debt held by Ontario Hydro, primarily the cost of building nuclear plants.
The Liberals and Conservatives both plan to continue the expansion of Nuclear energy in Ontario. Only the Ontario NDP and Green party committed to not building more nuclear reactors.
Edited to add Greens in line above.