This forum thread and this one should answer that question.
I have an Alienware x51 r2 with a 240w psu.  It is running a 4th Generation Intel(R) Core(T M) i7-4770 Processor (8MB Cach e, up to 3.9GHz, 16gb ram, 250gb ssd and am looking at installing a Asus GeForce GTX 1050 ti 4gb phoenix fan edition.  Is the 240 psu enough for this setup?   If I need a new PSU, can I run at 780p in the interim and scrape by with my 240psi until a new PSU arrives?  Thanks
X51 R2, enough power?