Introduction
What you see before you, is a SeaSonic G-series 360W power supply with a 30amp single-rail powering a mid-range gaming system: Intel Core i5 3570, 16GB Crucial DDR3 memory, Intel 520-series SSD and an EVGA GTX 760 4GB.
When you go to a graphics card manufactures' product page and browse through their selection of GPU's, you might as well check out the minimum/recommended reqirements. Let's pick the GTX 760 as an example; a 500W powersupply with 30amps on the 12V rail is required/recommended by Nvidia and probably all of their partners. Should you get a 500W power supply - or maybe even a 600W unit - just to be sure it will work out alright?
Let's look into things...
It depends on a few things: If you want the ability to add a second GPU later on, get a beefier power supply. If you want to overclock your system, you should look into a beefy power supply. If you want your computer to be powerefficient and you're not planning to do any crazy stuff with it, do not get a beefier power supply. In this case, try and look the other way around!
Here is a review of the MSI GTX760 TF OC provided by bit-tech.net. Here we will focus on total system power consumption: http://www.bit-tech.net/hardware/2013/07/04/msi-geforce-gtx-760-twin-frozr-oc-2gb-revie/8
Test setup: Intel Core i5 3570K @ 4.2GHz, ASUS MVE board, 2x 4GB Corsair 2400MHz DDR3 memory, Samsung SSD, Lepa 1600 watt power supply and of course the video cards. We can already conclude from the specifications that the test setup bit-tech.net used for the review is more powerful and thus more powerhungry than mine.
Idle load is 105W. Peak load is 286W. Isn't it quite obvious and self explanatory? This is why I only use a 360W unit. If you know a gaming system like this will fulfill your needs, then why would you "go overkill" by picking a 500W power supply when a 360-450W will do just fine.
Let's get to the point
Quality over quantity, my friend. Most people who don't have much experience with PC building often buy cheap (and in some cases non-branded) power supplies which are nothing but garbage. Seeing Nvidia (and many other companies) recommending a specificly required power output for their products is very common, but also a misunderstood concept by many experienced PC builders.
I may be able to run this system with my Seasonic power supply, whereas Anon with "GIGAWATTZ-2000 360W XTREME GAMING"-power supply might not be able to make it, and this is why we see companies recommending what I would call "overkill". It's a safety the for the consumer.
Conclusion
I know I sound like a broken record, but make sure you buy quality when it comes to power supplies! Seasonic, SilverStone, Corsair, Antec, Cooler Master, Enermax, Fractal Design, EVGA, XFX and I could go on. If you're reading this, it is most likely that you are familiar with these brands. As long as you go for a solid & high-quality PSU, then I can guarantee you, that you don't need the amount of wattage that is being recommended by the companies.
Next time you're looking for a power supply, I want you to at least remember this recipe:
- Estimate a total powerdraw of what the system will peak (note that actual powerdraw is not TDP!)
- Add +30% to your estimation and find a good-branded PSU in given wattage-range.
- Amps are more important than wattage!!!
- Make sure you pick a power supply with the latest features and technology. Look for 80+ certified PSUs from Bronze to Platinum.
- Don't be affraid to buy an expensive unit. The best are often overpriced. Find the balance!
- READ REVIEWS OF THE PSU YOU'RE CONSIDERING! You don't want the PSU to be good, great, value or decent. You want it to be excellent, suberb, "editors choise", golden award, 100% kickass.
I hope you enjoyed reading this post, and you will take my advice and share with others. Feel free to post any question and/or feedback in the comments.
tl;dr - don't cheap out on power supplies!