sentences:  In particular, after a lengthy outage during summer, all buildings will be warm, and if the power were restored at once, the demand from air conditioning units alone would be more than the grid could supply.In colder climates a similar issue can occur in winter with the use of heating devices.In a larger grid, black start will often involve starting multiple "islands" of generation (each supplying local load areas), and then synchronising and reconnecting these islands to form a complete grid.