We can't calculate any values without having technical specs of the lamp.Unfortunately, I do not have the LED rating or the technical specs and neither is the seller. It comes with 1 LED light and 1 Reduction Voltage Module. Was informed it's low power consumption.
Power LEDs consume more than 20 mA to generate a bright light. If we assume each needs 40 mA, your lamp consumes 40*24= 960 mA that is almost 1 Amp at about 1.5 V, consuming 2.5 watts. Voltage step down circuit may have efficiency of say 60%, so your consumption is about 2.5/0.6 = 4.2WThat head lamp led actually has 24 LEDs on it if it's like mine.