Flexible resources aids in enhancing the resilience of a renewable dominated power system. Space heating systems equipped with heat pumps is one such flexible resource. With this background, the current study deals with the quantification of flexibility potential of space heating systems in houses equipped with various heat pump types. A heat pump model is represented using a vapour compression heat pump cycle.

This model is integrated with a thermal model of a house to estimate electricity consumption, for maintaining the indoor temperature at a set value, as flexibility quantification depends on electricity consumption. In addition to this, flexibility potential is quantified by, analysing and incorporating the results on minimum acceptable indoor temperature from twelve interviews with households owning heat pumps, into the integrated model. The results from interviews reveal that, there is an uncertainty in minimum acceptable indoor temperature, as it is dependant on a number of factors such as frequency and duration of interruption, access to additional heating and motivation to be flexible.

Hence, to quantify flexibility using thermal simulations, the indoor temperature is reduced from 20 °C to values between 18 °C and 15 °C, based on minimum acceptable temperatures stated in the interviews. The flexibility potential is quantified in terms of an instantaneous reduction in electric power and reduction in electric energy. By reducing the indoor temperature from 20 °C to the aforementioned values at an outdoor ambient temperature of -5 °C, in about a million single family houses in southern half of Sweden, an instantaneous reduction in electric power is estimated to be 1.6 GW, for the power system with 23 GW plannable power.

Additionally, considering the recovery of the indoor temperature to 20 °C in 24 h, electric energy reduction is found to be between 4.06 GWh and 7.4 GWh, when the reference indoor temperature is reduced to values between 18 °C and 15 °C respectively, over 17.25 h. Furthermore, with time the amount of flexibility offered reduces, becomes negative during the recovery period and finally reaches zero, when the indoor temperature is restored. The results reveal that space heating systems in houses equipped with heat pumps have the potential to enhance the resilience of the power grid during severe grid disturbances.