Regarding 13h vs 22h battery life - I wonder if c't did any test with manually enabled SATA power management? This is a big deal on recent Intel hardware and unfortunately is still not enabled automatically by linux kernel, as described here:
Some people know how to tune and others just want to work on the laptop. As this one comes with Ubuntu pre install, in my opinion, Canonical should provide a patch or script to Dell which tunes this on par with Windows out of the box instead of having the user do it. Seems MS arranges aggressive powermanagement out of the box for Windows so Ubuntu should have the same. This is an example of the wrong way around anyway; you should not have to install and run powertop etc ; you should have to deinstall it if you do not want it... IMHO that it. I use powertop and some of my own scripts on my X220's (my go-to laptops for years now and hopefully years to come) and I get the same battery life as Windows on it.
That is a very good point. I would go even further and say that Canonical, too, shouldn't have to apply patches. That's upstream kernel's job.
But here's the rub - on some hardware enabling SATA PM can sometimes lead to various weird bugs - from failure to boot to crash with blank screen after few hours of working perfectly. And Intel would't release any sort of documentation that sheds any light on why that is the case, and what should be done to avoid it. Intel does know what to do, since (sic) Intel's storage drivers do the right thing on Windows.
Which brings us to even stranger point: Intel apparently doesn't share this documentation with Microsoft either. Hence new laptops with pre-installed Windows ship with Intel's storage drivers, while installing vanilla Windows 10 with Microsoft's storage drivers will give you as bad a battery life, as you get under Linux. This is an issue important enough that some laptop vendors employ hardware tricks to make storage hardware "invisible" for normal Microsoft's drivers for no good purpose other than to enable Intel's driver take over this hardware smoothly. See for example recent "Lenovo fake RAID" debacle:
That is not quite the same thing. Andy's NVMe patches allow drive itself to go into deeper power-saving states, while discussion above was about power-management of SATA controller which is part of PCH (earlier known as northbridge), which in turn, on last 3 generations of Intel CPUs is integrated into the same die as CPU itself.
Unpleasant side-effect of SATA (or NVMe) controller being integrated onto the CPU die is that it now shares a power domain with the rest of the chip (i.e. PM being present or absent on SATA controller affects allowed set of C-states for the whole package). In other words, as long as SATA controller don't go into deep sleep (i.e. never - without power management enabled), whole CPU+PCH package would not go to deeper C-state. Thus, lack of PM in storage controller has disproportionately high effect on the total system power consumption.
Thanks that is very informative (as is your followup comment). And also it is kind of depressing; are there vendors more open or does that just not happen?
They do not explicitly mention link power management, but I'd be surprised if they were not aware of this, since I remember this issue being mentioned in c't several times. They did ask Dell about the discrepancies in power consumption, and Dell says that it's mostly due to the new Kaby-Lake Intel GPU, which is not yet properly supported by Linux, and that probably the combination of Xorg and Unity draws more power than Windows.
They were able to reduce power consumption by 0,7W by setting i915.enable_psr, but that settings lead to temporary freezes of the screen.
http://mjg59.dreamwidth.org/42156.html
Easiest way to enable this is to run "powertop", switch to "Tunables" tab, then toggle all lines that look like this: