I'm sitting in the office on night shift and it's a quiet night so I counted the light fixtures in the main office area.
There are about 338 double T12 fixtures. A T12 bulb is 40 watts, so this comes up to 27kw of lighting. I'm going to round down to 24kw to account for burnt bulbs, or any that may have been retro fitted with T8 or maybe even LED. Some may also only have one bulb installed. Most have covers on them so I only based my info on a few that were visible but I assume that are all the same fixtures. I have a feeling most are T12 and never been changed to something else.
24kw is also equivalent to an entire residential 100 amp service being run at 100% capacity (100a x 240v). So it's a nice round figure to work with.
It just so happens that the off peak hydro rate of 7.4c/kwh is exactly between 7pm and 7am which is also the same time a night shift falls in so that makes the cost easy to calculate.
(24kw x 7.4c x 12h) / 100 comes up to $21.312 per day, or $639.36/month.
That's how much money they could save if they let us work at least our night shifts from home as typically the lights in this building are turned off if nobody is in here but now that we got moved here that changes. At the other building our office area had maybe a dozen fixtures and they were LED.
Things get more interesting during the day because of mid peak and on peak. Mid peak is 10.2c/kwh and on peak is 15.1kwh. On peak constitutes 6 hours while mid peak constitutes the other 6. It's split up but that's irrelevant for the calculations.
(24kw x 10.2c x 6h) / 100 comes up to $14.688 per day for mid peak hours.
(24kw x 15.1c x 6h) / 100 comes up to $21.744 per day for on peak hours.
So 12h day shift costs $36.388 per day, or $1,091.64/month.
In total, to keep the lights on for 24h in the office costs $1,731 per month!
That's just in the office area, I did not count the garage or bathroom or lunch room.
It's safe to say that if the company let everyone work from home full time they would save quite a lot in hydro.
God forbid we want to expense a box of pens though.
EDIT a few months later: Heard a rumour they are looking into replacing all the fixtures with LEDs.