Gaming laptop power consumption compared with desktops

Mar 5, 2018
I just bought a gaming laptop (Dell Inspiron 15 5000 Series) and just realized how small the power supply is. It has a 135 Watt capacity and comparing that to typical desktop of 600+ watts this is tiny.
I understand that most laptop parts are under specs than equivalent desktop parts. Mine comes with a gtx 1050 and i5 7300hq. The mobile version of the 1050 probably uses a bit less power than the desktop version and the cpu is definitely not as power hungry.. but the laptop has a moniter as well.
I guess my question is how do they achieve this? For instance, will I still be able to use the laptop off just the power cord without the battery pack installed?