This research identifies a specific and general operational problem of an inability to design human-computer systems effectively. The technical problem is considered a lack of suitable Human-Computer Interaction (HCI) knowledge. The long-term technical solution is considered to be the development of 'engineering principles', as proposed by Dowell and Long (1989). The technical aim of this research is to make progress towards these engineering principles. 'Engineering principles' for HCI are considered the knowledge required by an engineering conception of the discipline of HCI; it is knowledge that offers a guarantee of application. The thesis conceptualises engineering principles and describes a strategy for their development. The strategy involves cycles of development of human-computer systems using current HCI best-practice, which, in this case, includes the application of a structured Method for Usability Engineering (MUSE; Lim and Long, 1994). To assess the strategy, two domestic energy management systems are developed and examples of initial engineering principles, for domestic energy planning and control, acquired. The engineering principles are considered 'initial', since they have not been validated by application. Further, the status of these examples of initial engineering principles is considered 'early', requiring generalisation by further development cycles. The strategy is considered successful, given the early status of the initial engineering principles acquired. This research is concluded to have made significant progress towards engineering principles. Given the success of the strategy, a version of MUSE, termed MUSE/R-MUSE for Research, is presented to support further engineering principle acquisition and validation. Shorter-term research products are identified and further research is outlined.