As I did not have the numbers fresh in memory (apparently I needed a refresh ;) ) I googled for dram data sheet and got the first ddr3 PDF (Hynix). Quick, and very dirty math suggests that
-refresh power is on the order of milliwats per Gigabyte
-memory access is on the order of 0.1W per GB per second
For refresh power, let's face it: it's puny. Regarding the active power, I have yet to see anything (off chip and this size) that is better than that.
you overlooked refresh time, which is around 7~8 ms. So, in order to keep the DRAM data alive, DRAM should consume a few tenths of Watt per Gigabyte per second, it is considerable amount of power.
-refreshing is way (way) cheaper than streaming data out since you refresh an entire word line, and you do not pay io cost, which is a significant fraction of the cost of accessing dram.
-refresh power is on the order of milliwats per Gigabyte
-memory access is on the order of 0.1W per GB per second
For refresh power, let's face it: it's puny. Regarding the active power, I have yet to see anything (off chip and this size) that is better than that.
P.S. I did say active in my original post :)