High load since upgrade to 15.04

[Alvin]

Since the upgrade to 15.04, my battery is emptying faster than usual.
This is simply because the load is much higher.
(Yes, I'm also using the kubuntu-backports PPA)

I'll put a screenshot here for a while:
https://owncloud.alvin.be/index.php/s/bq6af7SkRVa5Soy
Load average is 2.24 2.06 1.96
Way too high. CPU is an Intel i3-3227U. I'd expect the load to be below 1 as 
it was on 14.10.

It looks like plasmashell and X are hogging the CPU, but why?

Are there people who can confirm this, know a solution, or can point me to a 
bug report?

Also, the new 'Energy Consumption statistics' do not reflect this. plasmashell 
and X can't be seen in that list.