It's been my practice to buy the biggest PSU I can afford, within reason, so I am using around 50%-60% of its rated output on max.
It would be better for the sake of maximum average efficiency if your
average PSU load were around 50-60%, not your
max load:
On PSU Efficiency
PSU "50% Load" Myth
You also will have some wiggle room when you do want to upgrade without having to add another PSU to the cost.
With the way things are going, each new generation of CPUs and GPUs requires less power than the previous. In some cases, almost the same, but not more. So it would have to be a pretty big upgrade...
A bigger one will also let you play what you want or do tasks without worrying about whether or not the PSU will stand up and not overheat.
Good quality-made PSUs like yours and mine, as well as pretty much 90% of the PSUs on the list below, will have absolutely no problem with heat or anything else because they're designed to easily deliver their rated (continuous) wattage 24/7 if it's ever needed. Most of them are rated to do so at an internal PSU temperature of 50°C. A few are rated for 40°C, and even fewer are rated for 30°C:
FAQ: Recommended Power Supplies
The only kind of PSUs you have to worry about for the kind of things you're talking about are PSUs that are generally never recommended by any of the PSU experts (and for good reason). So having a PSU like the HX650 for a system that will never pull more than 300-350W from it is absolutely unnecessary overkill and it reduces your average efficiency to
below what's advertised. With your PSU, your system could be set up so that it pulls 500-600W from your PSU while gaming and it would be just fine because it's designed to
easily deliver 650W 24/7 if it's ever needed, and it's rated to do so at an internal PSU temperature of 50°C.
I checked PSU recommendations for various GTX 650 Ti's and of those which listed a PSU minimum, EVGA and Galaxy, both stated a 450W minimum PSU is recommenced. Another brand, Zotac said 650W.
I do own a Rosewill 500W PSU and it performs as it should.
Those recommendations are for peak-rated PSUs, not continuous-rated units like ours (or
any of the units on the list of recommended PSUs for that matter).
Take a peak-rated 450W PSU for example. The +12V capacity would be at around 324W, which is 27A. Now, today's systems draw most of their power from the +12V rail because most of the parts in a modern computer run on 12V power. So a peak-rated 450W PSU with a +12V capacity of 324W means that it can likely deliver about 350W continuously, although probably rather poorly because no good quality-made PSU is peak-rated. Either way, having a +12V capacity of 324W means that it could be sold as a 350W continuous-rated PSU just like how the HX650 is sold as a 650W continuous-rated PSU.
Now, I don't know why or how Zotac would recommend a 650W peak-rated PSU to power a system that has one GTX 650 Ti in it because a peak-rated 650W PSU would have a +12V capacity that's no greater than about 480W, or 40A (and that's being slightly generous). There are a few quality-made 520W PSUs on the market that have a +12V capacity of 480W/40A. So, unless Zotac's GTX 650 Ti pulls about 100W more than all other 650 Ti's, that 650W rating has to be for 2-way SLi.
I apologize for all of this, but I know that these posts are publicly accessible without a SevenForums account, and so as long as I'm around, I want to make sure that the information is as accurate and as correct as possible.
lol
