I can only tell you that surestops take less than 1/3 of an amp, per unit, WHEN the are activated (meaning the row unit is OFF, no turning of seed meter) So, 12 x 1/3 = 4 amps total, if all 12 rows were OFF. (4 amps isn't much.)


I have them on a JD planter, and my monitor buzzes, when I shut one row off (all mine are operated manually), but I can also silence, the monitor, too.  


http://www.agleaderdealer.com/ag-leader-surestop-clutch/