An optimal mix is probably an unreachable grail, but a proper balance of environment protection, economics and reliability of energy supply, would help make sustainable choices. These impacts are not limited to headline figures of GDP, but include long-ranging effects and consequences on public budgets, the labour market, wider social indicators, health, environment and the competitiveness of the private sector. Models are needed to integrate all these effects, as a way to internalise them and to provide an insight into trade-offs and complementarities that exist between policy objectives in different domains.