Now that we have a significant source of electric power - the diesel generator - we will be tracking electricity usage in a quasi-realistic way.
For now, this will be done through the innovative, highly immersive method of: a Google docs spreadsheet. We're in beta, shut up.
Here's the link:
Have a look. Since I did this at the last minute, I didn't have time to write instructions, but I can explain it on-site. Hopefully, it's at least somewhat intuitive.
This should be considered to be a simplified version of the in-game spreadsheet the engineers are using, in addition to being the tool the the GMs will use to determine if the lights will turn on or not.
It is, of course, subject to ret-conning after playtesting. See above comment about beta.