A method for optimizing a production unit, which unit is a unit or a group of units in a papermaking, cardboard, or converting process. The method comprises the steps of analyzing the initial production features, determining the objectives of the production performance, determining the means for upgrading production and determining the upgrade package composition making an agreement with the customer for the means for upgrading production whereby the agreement comprises a step of the customer paying an investment fee (SP) of the upgrade package and a cumulative fee P.sub.cum covering the rest of the payment to the vendor.