So if you have a PC with a Sandy Bridge CPU without a discrete graphics card, one optical drive, a couple of fans and an SSD then how big do you need your PS to be? Certainly 300W is more than enough, isn't it?
And isn't it a bad idea to get a 500W+ PSU if you only are using less than 50% of the rated wattage?
It depends. Cost, noise and efficiency at idle/load are all factors.
And won't systems like this become more prevalent as Sandy Bridge CPUs become more mature and SSDs continue to get cheaper?
My theory is PSU inflation started when the GPU mfgrs started getting a lot of false returns. The real culprit was a PSU that might or might not have met the ATX spec at the time, but failed to provide enough/stable 12V power to the GPU card. Since they had no control over what PSU the consumer had in their computer, all they could do was inflate the required/recommended power rating, hoping by completely over-specifying the PSU, the darn thing would supply enough 12V current to meet the needs of their power hungry cards.
Move forward 5-10 years.
- ATX spec is revised with beefier 12V current.
- 80+ (and then Energy Star) requirements drove changes in PSU architecture.
This has led to better PSU designs/implementations. So, the fake need for a 500W PSU turns into smoke. Unless you have a high power 2 GPU setup.
That's the supply side.
On the demand side, all of the hardware uses a LOT less power for a given task. So, a Sandy Bridge setup w/o a separate GPU uses less than 100W.
The problem then becomes:
- PSU mfgrs make more profit on higher wattage PSUs.
- Meeting 80+ at 20% load is a difficult design at lower wattages. That's why the lowest you see from a mfgr you'd want to buy from in the ATX form factor are ~300W and more.
- Consumers are mostly idiots and believe what they read on the interweb/bathroom walls/what their BFF tells them. So, high power PSUs must be good!
- review sites perpetuate the PSU myths.
So, not a lot of incentive for the PSU suppliers to drive lower wattage products out the door.
Net result, we end up looking for the best 300W for our desktops and idle power stifles at 20-30W, when it could be 10W. In the end, this may drive me to getting a laptop to use for an HTPC. Similar specs, half to 1/3 the idle power.