In principle, all electricity used in a house eventually ends up as heat. Based on the quantity and the usefulness of supplied heat energy, an appliance can be qualified as source of internal heat gain. Although the internal heat gain sources are well understood, there is little research into quantifying the gross household internal heat gain with respect to high resolution time series data at per-minute intervals. Moreover, the impact of demand response (DR) programs in building heat energy demand dynamics has not been investigated fully. Through the combined utilization of engineering and statistical methods based on high-resolution appliance level household load models, we were able to reveal the underlying dependencies between internal heat gain sources. The results show internal heat gain amounts between 5% and 7% from the daily heating energy demand in typical single-family detached households on a cold winter day. In addition, the practice of DR programs on the non-heating loads affect the household environment by flattening the indoor temperature to a steady value and by reducing the frequency of bang-bang switching of direct electric heaters.