I am looking to upgrade all the Mears stats in our townhouse, each room is on it's own zone, circa 1988. After reading a few Help Desk queries about the Mears I am now confident in looking to upgrade to a digital programmable stat.

Question: Newer programmable stats are asking Capacity and Wiring questions. Example:
Wiring: 4 wire DPST
Capacity: 3600 watts @ 240V

Based on the information I was able to gather off the existing stats in my home how would I determine what type of existing wiring? And what existing wattage? So I may upgrade to the correct and more energy efficient stat? Thanks.