HP Pavilion Desktop PCs: Power Supply Power Ratings

[Technetium-99]

Hello to the HP community.

I must warn you all, this is a long thread and is potentially confusing, so only read this if you're interested in giving feedback.

I am here today to not ask a question, but to share with you my confusion on your Pavilion desktop PCs. I've looked at the technical specifications for many of the Pavilion desktops, including my own, and I simply can't understand one thing; where do you get your PSU power ratings from?

I currently have a Pavilion 500-319na: http://support.hp.com/us-en/document/c04343438.

It's a good computer, powerful in most areas although the GPU isn't, so I'm looking to upgrade it. The first thing I check before I upgrade parts, and hopefully others do too, is the PSU's power rating. And this is where my problem lies. Firstly, your website states that for my PC, and others, it's an external power adapter. It simply isn't, as it's inside of the PC. I've seen in many discussions that this has confused people, including myself. And secondly, your website states that for many of the Pavilion PCs, including mine, the PSU is rated at 180W. Let me tell you why I believe is wrong:

• The PSU that comes with my PC, and presumably other Pavilions too, has four power outputs: 3.3V (12A) and 5.08V (10A) outputs, 'limited' at 70W. Then there are 12Va (7A) and 12Vb (10A) outputs. These apparently produce 180W. First of all, the 3.3V and 5.08V outputs can't be limited to 70W, in theory. This is because, using the equation P = VI, the outputs are actually producing 90.8W. 90.8W added to 84W (the power output of 12Va) equals 174.8W, which sounds good if the PSU was 180W altogether. But...
• This leads me onto my next point. You may be wondering why I didn't mention the 12Vb power output in my previous point. This is because, I believe, it has been missed out of the power calculation. This output produces 120W. Added to 174.8W, it gives a total of 294.8W. So this makes me wonder, is the PSU actually 300W, but with a miscalculated power output?
• And, again, this leads me onto something else. The GPU in the machine is a GeForce GT 705. The minimum PSU wattage for this GPU is 300W. So, how can this GPU run on 180W? 

HP, please don't say that the PSU is external on your technical specs, because it's internal! A simple but crucial piece of information when discussing hardware upgrades. And secondly, please make sure you get your power calculations correct, because in theory the PSU cannot be 180W. It's just too low power for desktops you claim to be high performance.

Thanks for reading everyone.

[Big_Dave]

@Technetium-99

HP doesn't  have an official presence on this forum other than for administration and moderation. The assistance that you receive is mainly from volunteers.

Current limiting circuits have been in power supplies for quite some time. So, output current can limited and will be by internal taps.

If HP has limited the 12V to 12Va without a physical connection to 12Vb then the calculation would be correct.  Did you consider the efficiency rating into your calculations?

HP has been categorizing PCs into a common series. That practice has brought up numerous confusion posts on whether the PSU is internal or external as the documentation doesn't reflect both situations. However, other HP information does show the internal PSU but also * to show that some models are configured with the external PSU.