This is to be expected with newer versions of every software. Take just-released versions almost like beta... It's fact BitDefender should not release a buggy, maybe incomplete version of their antivirus, but there are lots of factors that could influence this scenario, like killing Windows Update, new Microsoft Security policies on Windows 10, etc..
My suggestion would be uninstalling and using a previous version or tweaking BitDefender for less protection to make it consume less. Else, ask for a refund but i personally would not.