The RESONANCE project aims at making it as easy as possible to tailor Customer Energy Manager (CEM) solutions for consumer and prosumer customers in different sectors. The CEM represents a fundamental change to the role of consumers and prosumers from passive recipients to active participants in the cross-sector energy ecosystem. In this regard, the CEM concept has the potential to revolutionise demand-side flexibility management and enable new consumer-oriented services. CEMs are envisioned to 1) provide a more deterministic demand response which is needed for predictability and 2) optimise consumer benefits with respect to multiple incentives and goals. To achieve this, there is a need for accurate models of the smart appliances and model predictive control techniques to automate the decision-making within the customer premises.