The only hand soldering system that is available where you can measure power is the OK International line of Metcal soldering systems. This system uses a fixed temperature variable power soldering cartridge. In operation, you would connect a net power meter in line with the soldering iron. Once the tip stabilizes, any load placed on the tip will cause the system to deliver more power to the tip in order to maintain the tip temperature. This increase in power will be displayed on the meter.