Local governments and property developers are increasingly seeking robust models for strategic planning of retrofitting residential energy systems. Strategic planning here infers making decisions on technology upgrades at the concept design stage. This represents a problem with many degrees of freedom. Optimization models offer a solution. The presentation of the tool RESCOM is the focus of this paper, a MILP (mixed integer linear program) that builds upon previous models of urban energy systems and extends these efforts by incorporating both demand side technologies, and explicit spatial and temporal resolution. A test case for a London borough describes the result of applying spatial optimization and demonstrates the accessibility of this program to decision makers. Results provide the optimal configuration of supply side and demand side technologies required to satisfy thermal energy requirements for a range of scenarios. The presented approach solves retrofit problems at urban scale in an efficient and thorough manner, providing an expandable framework towards providing solutions for the selection and operation of complex energy systems. (C) 2013 Elsevier Ltd. All rights reserved.