This page shows how to determine power consumption of memory modules to help specify a system power supply. Here are some factors affecting memory power calculations:
3) There is only one active rank of memory per channel
To determine memory module power consumption, follow the steps below:
1) Determine total current draw
It is important to note that memory may briefly consume the most power during power up, resulting in a current surge on the power supply for a short amount of time. This extra current should be accounted for when choosing a power supply.