Since refrigeration is probably your largest consumer of power, and most
people don't *really* know how many hours a day their system runs, I would
suggest that you get a 12V run-hour meter and wire it into your system.
Log how many hours it runs and keep that in a spreadsheet and calculate how
much power you're using on a daily basis.

I do this and it lets me know how well the system is working and points out
any potential problems which may be forming. Since I designed and built my
system, I also have a tendancy to play with the expansion valve settings
and thermostat set-points. This allows me see how the changes have
effected the performance. I tend to go a bit overboard and keep track of
both the refrigeration and freezer run hours.

-- Geoff