Question: What is the earliest Year commissioned wiht an Average annual output greater than 58 and Installed capacity of 20?
SQL: SELECT MIN("Year commissioned") FROM "2-16183862-1" WHERE "Average annual output (million KWh)" > 58.0 AND "Installed capacity (megawatts)" = 20.0;

Question: What is the Average annual output for culligran power station with an Installed capacity less than 19?
SQL: SELECT AVG("Average annual output (million KWh)") FROM "2-16183862-1" WHERE "Name" = 'culligran' AND "Installed capacity (megawatts)" < 19.0;

Question: What is the Year Commissioned of the power stationo with a Gross head of less than 18?
SQL: SELECT AVG("Year commissioned") FROM "2-16183862-1" WHERE "Gross head (metres)" < 18.0;

Question: What is the Year commissioned of the power station with a Gross head of 60 metres and Average annual output of less than 59 million KWh?
SQL: SELECT MAX("Year commissioned") FROM "2-16183862-1" WHERE "Gross head (metres)" = 60.0 AND "Average annual output (million KWh)" < 59.0;