For a customer of industrial maintenance solution providers, purchasing a solution is an asset management option that needs to be justified, preferably in economic terms, e.g. by achieving energy savings or increasing the availability of a production system. Therefore, the value elements of maintenance service solutions should be identified and quantified wherever possible. When assessing customer value, one needs to focus on the assumed benefits on the basis of which the value proposition is made, on the value elements based on the capabilities and know-how of the service provider, and the features of the services provided. Even though research on customer value in product, service and solution management has clearly increased in recent years, a common understanding of comprehensive value assessment in industrial maintenance management is as yet incomplete, and new methods to promote value element identification and value assessment need to be studied. In our paper, we present an integrated methodology for assessing the value of a maintenance services. The approach combines a qualitative Service Quality Function Deployment (SQFD) method with a quantitative Service Business Value Assessment (SBVA). The utilization of the multi-method approach is illustrated by means of a real-world case study of a value-based assessment of the maintenance service portfolio of a provider of industrial solutions.