  The increased integration of variable renewable generation into the power
systems, along with the phase-out of fossil-based power stations, necessitate
procuring more flexibility from the demand sectors. The electrification of the
residential heat sector is an option to decarbonise the heat sector in the
United Kingdom. The inherent flexibility that is available in the residential
heat sector, in the form of the thermal inertia of buildings, is expected to
play an important role in supporting the critical task of short-term balancing
of electricity supply and demand. This paper proposes a method for
characterising the locally aggregated flexibility envelope from the electrified
residential heat sector, considering the most influential factors including
outdoor and indoor temperature, thermal mass and heat loss of dwellings.
Applying the method to England and Wales as a case study, demonstrated a
significant potential for a temporary reduction of electricity demand for
heating even during cold weather. Total electricity demand reductions of
approximately 25 GW to 85 GW were shown to be achievable for the outdoor
temperature of 10 degreeC and -5 degreeC, respectively. Improving the energy
performance of the housing stock in England and Wales was shown to reduce the
magnitude of available flexibility to approximately 18 GW to 60 GW for the
outdoor temperature of 10 degreeC and -5 degreeC, respectively. This is due to
the use of smaller size heat pumps in the more efficient housing stock.
However, the impact of the buildings' retrofit on their thermal mass and
consequently on the duration of the flexibility provision is uncertain.
