Consumption of energy for private and commercial purposes is a factor which has many effects in our daily life and thus on our environment and our society as such. And since energy can be produced by a variety of methods some of which have larger effects on the environment than other it is obvious to consider how the effect of the damaging methods can be avoided. But it is not possible just to change production methods over night as the existing power plants and the related distribution networks are of a considerable size so long term strategic evaluations must be carried out. Such considerations include e.g. when a new technological substitute with less environmental damaging effect can be expected to be available from a technological as well a commercial point of view. The presentatio focuses on how technological forecasting can be applied to evaluate the future performance of a potential substitute to an existing environmental damaging way of production. An actual example will include a strategic evaluation of the future potentiality in wind energy produced by windmills. The evaluation will be based on technological as well as economical factors in order to predict when the cost of energy production based on windmills will match the costs associated with the traditional burning of fossil fuels.