  To phase-out fossil fuels, energy systems must shift to renewable electricity
as the main source of primary energy. In this paper, we analyze how
electrification can support the integration of fluctuating renewables, like
wind and PV, and mitigate the need for storage and thermal backup plants. Using
a cost minimizing model for system planning, we find substantial benefits of
electricity demand in heating, transport, and industry adapting to supply. In
Germany, flexible demand halves the residual peak-load and the residual demand
and reduces excess generation by 80%. Flexible operation of electrolyzers has
the most significant impact accounting for 42% of the reduction in residual
peak-load and 59% in residual demand. District heating networks and BEVs also
provide substantial flexibility, while the contribution of space and process
heating is negligible. The results are robust to restrictions on the expansion
of the transmission grid.
