Typically, services are co-created by service provider and customer. This paper describes an approach to account the full costs of a service considering costs at the provider side as well as on the customer side resulting in a more accurate cost model. Depending on the level of integration of provider and customer, explicit modeling of uncertainty is used to reflect the uncertainty about customer’s competences. This model may help to improve the efficiency of services and whole service systems. We evaluate the model in a scenario derived from an industrial application.