CREATE TABLE table_18843 ("Autonomous Community" TEXT, "Hydroelectric power" FLOAT, "Wind power" FLOAT, "Solar power" FLOAT, "Biomass power" FLOAT, "Solid waste power" FLOAT, "Total Renewable Generation" FLOAT, "Total Electricity Demand" FLOAT, "% Renewable of Total Electricity Demand" TEXT)

What is the lowest numbered hydroelectric power when the renewable electricity demand is 21.5%?
SELECT MIN("Hydroelectric power") FROM table_18843 WHERE "% Renewable of Total Electricity Demand" = '21.5%'
SELECT MIN("Hydroelectric power") FROM "table_18843" WHERE "% Renewable of Total Electricity Demand" = '21.5%'