"Home Guy" wrote

..
The meter is in a locked cabinet. The only time I get to see it is when
the meter-reader guy comes around once a month to read it.

I suspect the meter is in a locked cabinet to prevent tampering / bypass
(the meter is inside the utility / furnace room of the building and is
not accessible from the outside).

And besides, having the ability to lay my eyes on the meter won't tell
me anything about the accuracy of the meter, or the real-time current
consumption.

All I want to know is - should the current readings from a clamp-on
meter (when extrapolated across the 730 hours of a typical month) jive
with the accumulated KWh reading as measured by a typical billing
meter? Do I have to do any "special" math to the wattage I calculate
with the meter to arrive at what the billing meter is measuring?

There is no special math, but I'd wonder just how accurate your number is
going to be. Don't for get about seasonal changes too, more lighting in
winter, AC in summer, etc. At work, I take readings on some of our
utilities daily, others, monthly, and can spot a trend when correlated with
material used on a given day, etc. This will often tip you off as to
problem areas and waste when you see aberrations from the norm.

Have you talked to the utility company? Some will do the work for you and
put a recording meter on the line for a week or two to get you want you
want. Your approach, of course, is in the interest of energy conservation.
They are big on selling you less these days.

Reading the meter on a daily basis would be a help to determine trends also.
Perhaps they will allow a window to the meter so you can take readings.