The financial evaluation of environmental protection investments has been neglected in business research so far. While financing theoretical studies increasingly focus on equilibrium approaches and market values, environmental economic works include non-monetary aspects in their assessments but often inadequately represent the payment levels. Heinz Eckart Klingelhöfer develops an approach to assess such investments in imperfect capital markets under uncertainty. This requires the incorporation of production economic contexts to identify the relevant cash flows for individual enterprises and to adequately consider the impacts of the framework conditions provided by environmental protection. By formally outlining the determinants of the marginal price of an environmental protection investment, insights can be gained for the calculation.