Adding power to my basement
You need more info that "energy thirsty heaters". Somewhere is a rating on the heaters, in watts, that will answer this question. If the sum of the two heaters is less than 2400 watts, the you can do what you want.
12/3 can be used to wire two circuits, also called a multi wire branch circuit. This allows you to pull one cable to do the job. 12/2 will require 2 cables to do the same thing.
If you use 12/3 make sure the breakers are on different poles.
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