This will be sort of a long answer. Cisco spec sheets that I've found so far only list peak power, so we have to go to the Energy Star listings for average in-use and standby power. So here's the list as I have it.
Host DVRs:
8642HDC: Peak power (spec sheet): 50W Avg. in-use power (Energy Star listing): 27.6W Standby power (Energy Star listing): 21.6W
8742HDC: Peak power (spec sheet): 35W Avg. in-use power (Energy Star listing): 23W Standby power (Energy Star listing): 18.3W
9865HDC: Peak power (spec sheet): 35W Avg. in-use power (Energy Star listing): 27W Standby power (Energy Star listing): 21.7W
Client receivers:
1642HDC: Peak power (spec sheet): 50W (No Energy Star listing found)
4642HDC: Peak power (spec sheet): 50W Avg. in-use power (Energy Star listing): 17.5W Standby power (Energy Star listing): 13.8W
4742HDC: Peak power (spec sheet): 50W Avg. in-use power (Energy Star listing): 17W Standby power (Energy Star listing): 13.9W
Hope this helps! 