Why is it that you are concerned about 25%CPU usage? Does that seem outrageous to you? Are you concerned about power cost? Does your system overheat?
Really, there is nothing wrong.
Set your WU settings at NEVER. Run WU manually once a month 2 days after the 2nd Tuesday. When you run WU, hide all WINDOWS updates that are not labeled security. Just one time, install GWX Control Panel. Easy as that. Your system will be fine and kept up to date by you quite sufficiently and your CPU can rest!