Analyzing Power Use: 80 Plus Bronze vs. Platinum

I’ve been toying around with updating my computer lately, and one of the topics I wanted to look at was the choice of power supply. For the most part, we’ve long since moved beyond the days where power supplies that cost under $60 are garbage. There are plenty of decent power supplies available, particularly if you don’t mind taking a step down from the latest and greatest in terms of efficiency. Anyway, I was helping a friend put together a new PC the other day and it got me curious.

First, let’s start with the system build he put together, with some input from me. Note that many of the parts were selected based on price and availability on Amazon.com, as that’s where he wanted to purchase the parts (with his Amazon Prime account). In some cases, prices have changed since the purchase a week ago, so shop around as needed. Also note that he used a GTX 780, but I’ve also run some power use tests with just the iGPU as well as with a low-end Radeon HD 7750.

Now I’m not equipped to tell you about the quality of voltage regulation, ripple, or anything like that, but I happened to have a 450W 80 Plus Bronze PSU that I could use as a comparison point, so I asked if I could take some quick measurements once the system was put together. He agreed, and I ran through a few typical scenarios, summarized in the table below. (Note that I had to use a Molex to 8-pin PEG power adapter in order to run the GTX 780 on the old Thermaltake PSU; everything worked, but that wouldn’t be a solution I’d be comfortable with long-term.)

For power costs, we’re looking at the worst-case scenario of leaving a system on 24/7, which really isn’t realistic unless you’re talking about a server. For a typical PC that’s on eight hours a day, using the US national average price for electricity ($0.125 per kWh), we’re looking at electrical savings of anywhere from $2.56 to $8.40 per year. That may not seem like much, but considering any decent power supply should last five years and you’re looking at $12.80 to $42 in savings. That’s for a $21 difference in upfront costs, which is much smaller than what we’ve seen in the past for the most efficient power supplies – and note that the price difference tends to grow substantially when you’re shopping for 800-1200W PSUs, though that’s perhaps a topic for another day.

For a system that mostly sits idle, you won’t quite break even by going with an 80 Plus Platinum power supply. However, if there’s a graphics card installed and you do a moderate amount of gaming you should eventually come out ahead. More extreme use cases (e.g. 24/7 Folding@Home) start to rapidly recover the initial investment in a quality power supply, and when you consider the reduced heat and noise that comes with having a more efficient PSU, it’s definitely a worthwhile upgrade. Not all 80 Plus Platinum power supplies are created equal, of course, but generally speaking the electronics and engineering required to get that certification also come with a higher level of quality than what you’ll find in lower efficiency PSUs.

As far as the above system build is concerned, I like most of the component selections, but I’m not totally sold on the case. The Silverstone PS07B looks nice enough, but getting all of the wires connected can be a bit difficult at times. The SSD location on the bottom in particular is a bit of a pain, and the power supply location at the top has some silliness to go with it. The PSU location appears designed to work with the PSU upside down (i.e. fan facing upwards and drawing in fresh air), but the manual for the case notes that if you have a PSU with a 120mm or larger fan, they recommend installing it with the fan facing down. I'm not sure that I've ever seen a PSU with a fan smaller than 120mm where you have ventilation through the bottom, but whatever. If you follow the manual’s instructions, that means the ventilation holes in the top of the case along with the magnetic dust filter are completely pointless. I ignored the instructions and installed the power supply in the most sensible manner for the case, but my advice is to look at some of the other good mATX cases.

The Silverstone PS07B isn’t a bad case, but it’s not perfect either, and for the price I think you can do better. (Apologies to my friend for his taste in cases….) For mATX, I’d at least give the BitFenix Prodigy M or Corsair’s Obsidian 350D a look. If you want a larger case, there are tons of options to sort through, depending on what you're after. Other changes you might consider include sticking with 8GB RAM (2x4GB) initially, going with a midrange GPU like a GeForce GTX 770 or Radeon R9 280X, and there are quite a few motherboard options to consider as well. The i5-4670K still strikes a nice balance between price and performance, and with a bit of overclocking you can stretch its legs a bit further.

Anyway, that’s my little two-for-one special for the day: a quick look at the difference in power use you can expect from 80 Plus Bronze vs. Platinum (obviously 80 Plus Silver and Gold will be closer in power use, but they’re also closer in price), along with a list of parts that I’ve recently used in a friend’s PC. If you have any recommendations or complaints with the build, sound off in the comments.