How to calculate the refrigeration load of a walk-in cooler?

Answer 1

Variables include ambient temperature, the amount and frequency of foodstuff that's put in it and, very important, total time and frequency that the door will be opened for access.

You can purchase either low initial cost with higher operating costs or a higher initial cost with lower operating costs depending on the refrigeration unit you purchase.

Check out this site:
http://www.mellcon.com/cold-room-unit.html

Answer 2

Pretty tricky to calculate. There are many variables. It would be much simpler to borrow a KiloWattHour-meter from your your local power company (and way more accurate).