CREATE TABLE table_11456251_5 (power_capacity__gw_ VARCHAR, number_of_generators VARCHAR)

What is the power capacity when the generators were 781?
SELECT power_capacity__gw_ FROM table_11456251_5 WHERE number_of_generators = 781
SELECT "power_capacity__gw_" FROM "table_11456251_5" WHERE "number_of_generators" = 781