Significant reductions in energy use and environmental emissions are demonstrated to be achievable when electrical utilities use cogeneration. Simplified illustrations of these reductions are presented for the province of Ontario, based on applying cogeneration to the facilities of the main provincial electrical utility. Three cogeneration illustrations are considered: (i) fuel cogeneration is substituted for fuel electrical generation and fuel heating, (ii) nuclear cogeneration is substituted for nuclear electrical generation and fuel heating, and (iii) fuel cogeneration is substituted for fuel electrical generation and electrical heating. The substitution of cogeneration for separate electrical and heat generation processes for all illustrations considered leads to significant reductions in fuel energy consumption (24-61%), which lead to approximately proportional reductions in emissions.