Currently one of the most significant problems facing electric power utilities in the United States is the explosive growth of electric space heating, which is expected to increase by more than 1000 per cent by 1980. The financial and domestic-load effects of this growth upon electric power utilities and a number of peripheral industries, are considered. The distribution of winter-peak and predominate summer-peak load areas throughout the United States is outlined; but the phenomenal growth of electric heating, is not expected to overcome the summer-peak loads. The problems that have arisen through poor temperature control practice, in domestic electric heating, are discussed; and the theoretical basis for temperature control in the electrically heated home is developed in depth. The economic aspects of poor temperature control practice, as they apply to American domestic environments, are studied in detail. Comfort criteria and recommended temperature control practice are stated, for American homes, and typical examples are given of the control performance currently prevalent in these residences. Using the data and recommendations presented here, new thermostats of economic-acceptability have been developed, and their test results exhibit performance superior to currently-available models.