Disagree with above conclusions. Looking into voltage is not enough. Memory uses 1.2V (ddr4 for e.g.). The more modules you have on the pcb (32GB vs 64GB), the more Amperes (A) it draws. Energy produced is Vots x Ampers (P=U*I) so yes more chips more power drawn. Also, the higher frequency, higher Ampere draw, so also more heat too. The only exception would be that you buy newer memory, better manufacturing process (less nano meter technology) so it draws less Amps, still 1.2V but then Power output is lower.
So my advice, buy faster and better and bigger memory, just try finding sticks using chips manufatured in newer technology which then draws less Amps.
Some evidence, experience, upgrading notebook to 3200MHt runs hotter than 2400MHz using identical Micron sticks, almost identical chips. Using even lower CL settings things get even more stable. Undervoling CPU is interesting too.