Just tested my 396XT using an AmWatt appliance load tester...
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Battery switch set to alkaline, power off: 2 watts
Battery switch set to alkaline, power on, backlight off: 6 watts
Battery switch set to alkaline, power on, backlight on: 7 watts
Battery switch set to NiMH, power off: 13 watts
Battery switch set to NiMH, power on, backlight off: 15 watts
Battery switch set to NiMH, power on, backlight on: 16 watts