This study deals with flexibility quantification from space and water heating in about a million houses equipped with heat pumps, for providing emergency power support in a renewable dominated power-system. As electricity consumption determines the flexibility potential, this is estimated using integrated physics-based models involving a heat pump, space and water heating. The flexibility estimations are between 2.1 GW and 0.5 GW, at outdoor ambient temperatures ranging between -10◦C and 10◦C respectively, for a power-system with a dimensioning fault of 1.45 GW. The reduction in electric energy is between 5.4 GWh and 3.2 GWh, when the indoor and water temperatures are reduced from 20◦C and 55◦C, to 18◦C and 50◦C respectively over 17.25 hours, considering 24 hours recovery period. Additionally, electricity consumption as a function of time serves as valuable information for power balancing. Furthermore, a modified Nordic-32 bus system with a high share of renewable power installations is proposed. In this system, the loss of a major generation corresponding to 12% of the load, causes an instantaneous frequency deviation below 48 Hz. This can be limited by providing emergency power support using house heating flexibility corresponding to at least 5.9% of the load.