An iron with a power rating of 1,000 watts (W) transfers energy at the rate of 1,000 joules per second electrically. This is because power in watts is defined as the rate of energy transfer per unit time, with 1 watt equal to 1 joule per second. Therefore, if the iron operates at 1,000W, it transfers 1,000 joules of energy every second. In summary, the iron will electrically transfer 1,000 joules of energy each second it is in use.