I constantly have a cpu usage of around 20 to 25% on a boot camp installation of windows 7 64 bit. My machine is a Macbook pro Retina 13 inch mid 2014, model A1502. Under task manager, it's the "system" process which is the cpu hogger.
I've installed windows performance toolkit and ran an "xperf trace" to really find out specifically what is gouging all that cpu and found out it's the ACPI.sys driver.
By disabling ACPI in device manager, cpu usage was the same. I even reinstalled win7 and installed all windows updates and cpu usage was constantly around 20-25%. I'm guessing it's one of bootcamp's drivers not working properly with my mac's model, I could be wrong.
Anyone else having this issue ?