XPS 15 7590, fast on battery, slow on power?

If it's working that way, just leave it as is - that will do fine.

The question is always balancing consistent performance with flat-out performance -- there are applications where you can sustain speedup-slowdowns without much notice, but gaming isn't one of those.

And the laws of thermodynamics remain:  there is no way you can run a 3.x GHz or faster CPU at turbo mode for very long in any Inspiron or XPS system, which have slim formats and therefore limited heat sink capacity.  There's just no way to remove that quantity of heat from the system in anything like real time.

Thanks for this, I switched it down to good proformance rather than best and it runs as expected now. I guess it feels a bit odd buying an expensive laptop and not having it on best performance. Feels like I'm not sure if I'm getting the most out of it. 

I just changed it via the slider on the battery options on the task bar, is the best way to do or are there other ways of changing the settings to be best optimised?

Note that if that were the case, the system would run equivalently on battery and AC power -- when the AC adapter is not properly sensed, the system will run as if on battery full time.  It clearly is sensed here -- it's just that these systems cannot run at boosted speed for any length of time without reaching the thermal-throttling setpoint.

@dustmite  The other possibility is that your system isn't properly detecting the wattage of the attached power adapter, either due to an issue with the power adapter or the system.  If you want to check this, go into your BIOS to the "Battery information" section.  Under the battery graphic you should see the identified wattage of the attached power source.  Make sure it says 130W.  If it says Unknown, the system will reduce its power consumption as much as possible to minimize the risk of drawing more power than the "unknown" attached power source is designed to provide.  And those power consumption reduction steps involve significant CPU and GPU throttling, as well as slow or no battery charging.  Or if you're using a properly identified power source that's less than 130W, that can cause the same issue to a lesser degree.  Some people use XPS 15s with 60W USB-C power sources.  The system will operate with them, but at lower performance, because you're using a power source rated for less than half of what the system is designed to have available.

Thanks for your help. This makes sense.

It helped me a lot. Thanks!

Hi I experienced the same issue. But try to change but don't know where. Please help