Energy is force times distance. KWH is energy. Put a watt-meter on your machine. Next you need some way to calibrate this in terms of tonnage. One needs to work with the same lift height. You also need the no load energy and other losses.
As an alternative. Measure the current for an empty load and we will assume you always operate at constant velocity. Then measure the current for a known load. Assume voltage is constant. Load current minus no-load current is actual current from the load, and this should be approximately equal to the amount of load. Create a calibration constant from current to load.
Measure current for each load. Add all these up that occur in your desired 1 hour period.
If you have a meter capable of recording kWH then you can run the bucket elevator for an hour and record the tons moved as well as the total kWH. Assuming constant current and voltage you will have a kW power consumption that was used during this hour. Divide the kW consumption by your voltage to come up with a current for the tons per hour during that hour. You can then divide the tons per hour and the current to come up with 1ton/hr = x Amps.
This may not be the best way however due to the fact that currnent is not really linear with loading due to the changing power factor.
If you dont want to run this measurment for an hour you can run it for a shorter time and just scale the results to the correct units.