Residential buildings account for significant proportions of energy demand and greenhouse gas emissions. The dwelling and occupants together have a strong impact on the temporal characteristics of energy demand. This paper presents and validates a new stochastic electricity, space heating (SH) and domestic hot water (DHW) model for UK residential buildings, called CREST Heat and Power (CHAP). The open source model is easily adaptable to over 14,000 different building configurations, which represent the UK residential building stock. A validation with empirical data on domestic hot water, gas demand, and internal temperatures demonstrates the accuracy of the new SH and DHW parts of the model. Notwithstanding some uncertainties in extracting the DHW run-off profiles, the energy consumption, water volume, and the dependency on the number of residents are all well considered. The CHAP model produces mean SH, DHW and temperature profiles that are broadly in agreement with the employed field studies. Future work should focus on the consideration of appliances at the heat/power interface, improving the DHW calibration and extending the approach to other national contexts.