We describe how hardware description languages (HDLs) can be used to support the design and simulation of systems incorporating components interacting in multiple energy domains. This methodology encourages emphasis on higher-level system design while providing performance targets for lower-level component design. It can also be made independent of the actual simulation engine (special-purpose mixed domain simulators or separate simulators for different energy domains). This approach supports modular, hierarchical design and allows strategies such as rapid prototyping and component reuse to be applied to multidomain systems, thus speeding the development of such systems for commercial use.