This paper proposes three analyses of the tradeoff mechanism between ecotax and carbon credit. Our wish is to compare the ecotax level with the carbon credit price, subject to the minimization of the cost inherent to emissions. We redefine the calculus equations of the firm profit, in which we inject the parameters of energy intensity and emission intensity. We proceed to one static and two dynamic studies, whither we adapt the methodology of population dynamics. Our results highlight a simple tradeoff rule between ecotax and carbon credit, both in the static and dynamic models. In uncertainty, the rule determines whether the level of environmental tax is under- or overvalued compared to the carbon credit price. As well, the study enables to determine the global level of tax revenue attainable by the enforcement of the environmental taxation.