older servers had a peak to idle ratio of only 1.8 (average) compared to 4.8 average for the new servers.  This is not a surprise given the proliferation of power management schemes to reduce energy use.  Then I looked at the PSU power rating (all at 1N redundancy) and found that the new servers had a PSU rating that was on average 3.5 times that of the maximum server power consumption.  This was slightly higher than the average for the older servers which was 2.9.  One would expect that these ratios would be closer to 1.5 if server vendors were sizing PSUs to the maximum server load and maximum PSU efficiency.