This unit has a proprietary 180 watt power supply.  You can only purchase from hp.  I have been on the phone, email and chat now for 6 hours to purchase the 400 watt power supply so I can upgrade the graphics card.  Now I am advised that I can only email hpparts.sales.ams@hp.com and hope for a reply.I failed to read the return policy on this prior to purchase.  That is my fault.**** Update: I am been in the loop with HP for 5 days now trying to find out the information to purchase the Platinum 400W power supply  and GTX 1650 Ge Force graphics card.  No go! I have been transferred to management at every level for an apology with no resolution.  This is my first and last computer purchase from Amazon and my last period for HP.