Evidence submitted in January 1979 to the Ontario Energy Board, prepared for the Public Interest Advocacy Center on behalf of the National Antipoverty Organization of Canada. The author argues: Marginal cost pricing of electricity is feasible and a sound basis for ratemaking, and promotes economic efficiency, fairness, and financial adequacy. There is abundant evidence that electricity customers can adjust satisfactorily to time-of-day electricity rates, and that these adjustments are beneficial to both the utility and to customers in achieving lowered electricity bills. Time-of-day rates give customers opportunities for cost saving that conventional rates do not. In many cases it increases the competitive advantage of industrial customers to have time-of-day rates available. The line management proposal to create a "diversity benefit" subsidy and to apply it selectively to certain large customers constitutes discrimination in rate making not based on differences in costs of supply.