did an article on the subject of special, low voltage RAM. However, the difference is relatively minimal, since that probably translates into a difference of a few watts. Two sticks of course can consume 3 volts, regardless of total capacity. For example, a single stick of 4GB uses around 1.5 volts. The funny thing is that heat produced is dependent entirely on the NUMBER of sticks of RAM that you use, rather than the total size of RAM. You won't get dual channel mode (if your system supports that), but that's not a big deal anyway.
However, if you simply swap a 4GB stick for the 2GB, your heat and drain will decrease.
Your battery life will somewhat go down (in my experience, not really) if you add another stick of RAM.
