Hello SPCR,

I'm upgrading old Dell Optiplex GX280 for a friend that has 240 Watt PSU with 14 amps on the 12 volt rail. I'm looking to buy the cheapest, lowest power video card and my choices are the Radeon HD 5450, Geforce GT 210, Geforce 8400 GS. I know the system likely doesn't use more then 140 watts but I don't want it to go poof. My research says the Radeon HD 5450 uses between 9 watts idle, 19 watts load. I'm correct in assuming this lowest power drawing card out of the three?

From Wikipedia I found these TDP numbers:
Geforce 210 - 30.5 Watts
Geforce 8400GS - either 40 or 25 Watts depending on the transistor size. Later models made after 2007 are 65nm, the 2007 models are 80nm. If you're finding one for sale new it'll almost certainly be the 65nm, lower consumption revision.
Radeon HD5450 - 19 Watts as you found.

So if power really is everything, the HD5450 is the obvious winner in terms of TDP. Whether or not they'll each use more or less in this application depends. What is the system mostly used for?

Most load it will see is playing Mkv HD files with Core AVC. I want to install the video card to off load the processing onto DXVA . The 240 watts on the PSU is continuous output not peak load. I've upgraded similar systems with the same PSU and didn't have issues with far less power efficient components.

http://forums.atomicmpc.com.au/index.php?showtopic=264 hasn't been edited since early/mid 2012 but it's good data and still valid for the most part

5450 is 15w max
GT210 is 18w max
8400gs is 20w max

but that doesn't address performance, one of those cards could be 5 times faster than the other at the same power level so it's a whole different set of research to figure out if they are good performance wise

and a third discussion altother for hardware reliability and driver issues

oh and a forth discussion when it comes to price.

in short I'd avoid the 8400gs and pick the 5450 or gt210 based on price, physical size, preference between AMD/NVidia (my bias is for the 5450 for multiple reasons but its not the end of the world if you got GT210)

I would also avoid the 8400GS for another reason. The Geforce 8 series is now the oldest supported in latest NVIDIA drivers and in a few years perhaps support will end.

Also look to see if the older cards are supported by Core AVC.

Are you sure you want a card with just 32-bit or 64-bit DDR3? That's seriously low on bandwidth.