The Government of Ontario’s goal of reducing GHG emissions by 80% by 2050 is an ambitious but appropriate target given the high costs of not acting to curb our climate impact. However, it also means that we cannot afford to squander resources on high-cost actions, such as rebuilding 30-40-year-old nuclear reactors instead of investing in energy efficiency and securing lower cost renewable energy, particularly low-cost water power from Quebec. This report outlines options for reducing emissions from Ontario’s electricity sector at the lowest possible cost.