MacBook :: Power Consumption While Screen Brightness Minimum

How to calculate the regular MacBook power consumption if it is left on lowest screen brightness for about 12 hours, plugged in, with just a browser running Gmail? The following is the System Profiler->Power Information that pertains to this topic:

Battery Information:
Model Information:
Serial Number:DP-xxxxxxx-xxxx-xxxx
Manufacturer:DP
Device name:xxxxxxx
Pack Lot Code:0002
PCB Lot Code:0000
Firmware Version:0110
Hardware Revision:0500
Cell Revision:0102
Charge Information:
Charge remaining (mAh):4831
Fully charged:Yes
Charging:No
Full charge capacity (mAh):4831
Health Information:
Cycle count:188
Condition:Good
Battery Installed:Yes
Amperage (mA):147
Voltage (mV):12604

System Power Settings:
AC Power:
System Sleep Timer (Minutes):0
Disk Sleep Timer (Minutes):10
Display Sleep Timer (Minutes):20
Automatic Restart On Power Loss:No
Wake On AC Change:No
Wake On Clamshell Open:Yes
Wake On LAN:Yes
Display Sleep Uses Dim:Yes
Battery Power:
System Sleep Timer (Minutes):5
Disk Sleep Timer (Minutes):10
Display Sleep Timer (Minutes):1
Wake On AC Change:No
Wake On Clamshell Open:Yes
Display Sleep Uses Dim:Yes
Reduce Brightness:Yes
Hardware Configuration:
UPS Installed:No
AC Charger Information:
Connected:Yes
Charging:No