Vendors’ thermoelectric module (TEM) catalogs will show a typical range of commercial-off-the-shelf TEM products. Here is a link to an example: http://www.thermonamic.com/Pro_View.asp?Id=806
TEMs have a standard unit naming convention where the first three digits specify the number of thermocouples and the last two digits specify the maximum input current (Imax): the DC current that will pass through the module at DTmax.
For example, a TEC1-04902 module has 49 couples and has a 2 Amps Imax.
Other specifications in the catalog will include: Tmax maximum temperature change between the two sides; Vmax maximum Voltage; and Qmax maximum Wattage. Dimensions are in the column on the right.
Read Part 5 of this Tutorial - Module Datasheets: https://www.collaborizm.com/thread/BJBW9aaOZ
To see a Collaborizm project using thermoelectric modules, check out Cool India: https://www.collaborizm.com/project/SJVLyK2uZ