A load balance model is used to quantify the economic and environmental effects of integrating wind power into three typical generation mixtures. System operating costs over a specified period are minimized by controlling the operating schedule of existing power generating facilities for a range of wind penetrations. Unlike other studies, variable generator efficiencies, and thus variable fuel costs, are taken into account, as are the ramping constraints on thermal generators. Results indicate that system operating cost will increase by 15% to 110% (pending generation mixture) at a wind penetration of 100% of peak demand. Results also show that some mixtures will exhibit cost reductions on the order of 13% for moderate wind penetrations and high wind farm capacity factors. System emissions also decrease by 13% to 32% (depending on generation mixture) at a wind penetration of 100%. This leads to emission abatement costs in the range of $65 per tonne-CO2e for coal dominated mixtures, but $450 per tonne-CO2e for hydro dominated mixtures. For natural gas dominated mixtures, the introduction of wind power may well be beneficial overall.