The MSI 1050Ti LP is 182 x 69 x 35 mm

790 DT if using microATX motherboard is 244 x 244 mm.  Based on DT removal guide the card will probably fit.  Np in 790 DT with double slot width card.

if you use sata ssd (no hdd) and disconnect power from odd to save power, w i5-2500 + GTX 1050ti

Load Wattage: 246 W
Recommended PSU Wattage: 296 W

so if you have DT your 250w supports load w, and is 50w short of recommended 300w.  You will just get by.

A user showed successful run of GTX 1050 Ti in 790MT w stock 240w/265w psu. 

Load Wattage is the maximum wattage the system may consume in a typical real-world scenario such as running a modern 3D game with the majority of PC components operating at maximum load (CPU, RAM, Drives, etc.). Important: Load Wattage is not the absolute maximum wattage of the system. Various synthetic benchmarks may increase power consumption above Load Wattage levels.

What size/form factor is your 790 amd what CPU do you have?

Also, due to the age of the 790 and many questions answered already, have you searched within Dell Community or gone into Dell Community thru Google? 

@redxps630   More Bad Advice 75W card and Dual Slot.

Low Profile DUAL SLOT cards won't fit they are too thick.

WILL NOT FIT in case.

If you meant DT 790 by “desktop”, you can get a low profile GTX 1050 Ti with short bracket for up to $250.  DT psu is 250 w per tech guide.

if you have an i5 Sandy bridge cpu 250w psu will probably get by supporting 1050/1050ti.

The Blue Slot is the 50W slot and the Black slot is the 25W slot.

Tower can provide 25 Amps on 12v others 18 AMPS max for 12v which is 216W  on 250W power supply leaves 34Watts for everything else. Running power supply over limits is a recipe for a dead computer.

NOTE 75W only on Tower

Another happy user restored 790SFF with msi GTX 1050ti and 2.5” sata ssd (in odd enclosure).  

so if you meant SFF 790 by “desktop”, it is a go ahead too and np.

This is a Dell Optiplex 790 desktop PC

I'm going to transform this machine into a brand new looking, fresh out of the box PC complete with hardware upgrades to go with it. Then we're going to play some game titles on it to see how it performs.  Here's the graphics card:

Graphics Card Upgrade: Nvidia GTX 1050Ti

Make and Model: Dell Optiplex 790 SFF Spec: 2nd Generation i5 3.1GHZ 2 x 2GB 1333mhz 250GB Sata HDD 240W PSU Small Form Factor Thank you for watching this video today.

MSI GTX 1050 Ti low profile double slot width fits with ease in 790 SFF as shown in YouTube.  It is even easier in 790DT.

First, my oops in missing "desktop" in the subject line early on.

250 Watt Dell Optiplex 7010 DT Running 1050 GTX Ti / i5-2400 

Optiplex 7010 DT + GTX 1050 Ti (1080p Gaming

In this case, I'm in agreement with redxps630.  By the way, when I searched, 7010's came up.  Same PSU's as 790 except the MT.

My answers in regards to GPU's have the backing of Dell moderation, one of whom is a Dell engineer.  This is because 1. Some things, like 75w GPU's, have been working outside of past Dell specs in certain gens.  2.  No negative feedback from actual users, just positive.  3.  Quantity of YouTube videos showing that Dell's 240w-265w PSU's can too power 75w cards.  75w cards are not 18 amps.  I think somebody should analyze why it's working vs. not.

I also ran across a video in which the YouTuber tried powering a 120W 1650 SUPER or 1660 on standard Dell PSU.  Of course it didn't work.  It tripped the PSU.

@bradthetechnut 

"My answers in regards to GPU's have the backing of Dell moderation, one of whom is a Dell engineer."

Whom do you refer ? @Dell-BradL ?  @DELL-Chris M ?

The 25W max slot is known for many DT and SFF models.

Dell Engineering and the PCI SIG disagree as does UL 94v safety standards.  I have been on the forum for over 25 years and never have I seen someone refer to themselves as an Engineer.  Going against IEEE, PCI SIG, UL 94v saftety standards would never have backing from ANY engineer. I also disagree that DT and SFF  power supply is OK for 75W card.  MT is the only one that supports 75W card

Answers that 275w / 250w /235w are fine for 75w 1050 TI are bad advice at best and potentially dangerous advice at worst.

NOTE 305w unit power

25w slot

.Slot power is well defined