A strong focus on reducing carbon emissions as well as the improvements in computing and control techniques for energy systems make it relevant to design energy systems in an integrated way. Coupling various energy sectors can offer many benefits in the way of flexibility and better utilisation of resources and infrastructures. To illustrate the benefits of coupling the heat and electricity sectors, a general model for a domestic energy system is developed, and two simulations are performed of domestic systems with sector coupling technologies. Further benefits can be gained by optimising the two systems together, implying that it can be advantageous to take an integrated optimisation approach for larger numbers of domestic systems.