Ok, the prescaler is basically to sort out the variance from a shunt or measurement chip or whatever your measurement element is. It's ok though, I managed to figure out how to do it. This is my solution. After getting total amount of pulses over several hours, for calibration, this average value will be written to EEPROM upon startup/program. This average value will then be saved as my counter value in my EXT_INT. Everytime an interrupt is generated by the pulse from the measurement chip, this counter is decremented. Once this counter reaches 0, another counter is incremented thereby giving the WH (Watt Hour) value. Sorry if confused anybody. Thx for trying to help anyway everybody.