The discussion in the Super Flower PSU thread on 80+ methods showing results as percentages rather than heat loss and the tradeoff of cheap vs. efficient got me thinking. I spent some time data mining the SPCR PSU articles, throwing the test results back into Excel for some chart-fu.
First some caveats:
- Ignore differences of a few watts. It’s probably within the variance of the test equipment accuracy, the test setup, test repeatability, the phase of the moon, and how many craft beers Mike C and the other intrepid reviewers have consumed during the testing and editing process.
- These results span from Aug 2006 to Oct 2012. I’m sure there have been changes in the test setup during this time.
- Any discussion of power use is the DC power supplied by the PSU, not power at the wall socket.
- Curve fitting. Take it with a grain of salt.
- I’ve probably made a data entry error or two.
First up, the 14 most recently reviewed PSUs: 360W to 1050W, Bronze to Platinum, in one big eyesore of a chart. Data is plotted as power lost vs. power out. It’s a blob at 300W and below, but look at the higher loads and the variation in power loss.
Next, the same data zoomed in to look at typical idle, low CPU utilization and low power configurations. A new ATX desktop build can idle in the 20-25W range. These PSUs vary in efficiency up to 10W. Even going up to 60W load, the variance stays within 11-12W. A couple of things pop out:
- You can see the efficiency hit you take for using a higher power PSU than you need for low CPU utilization tasks.
- You can sorta see how low power efficiency has improved over time. Extreme example: Silverstone ST50NF with 16W power loss at 20W Power output vs. Kingwin LZP-550 with 6W loss @ 20W out.
Here’s a chart for high CPU utilization and typical (single graphics card) gaming builds. Some figures of merit: An i7-3770K system running Handbrake will be in the 100W range, a PC with a midrange GPU (HD 7850/7870, GTX 660/660 Ti) playing at 1080p can run from 100W to 250W. For this range, the variation in efficiency widens up. At 100W, the spread is 13W. At 200W, the spread is 20W. At 300W, it’s 28W.
To get a better look at efficiency improvements over time, the next series of charts compares all of the Seasonic PSUs reviewed (since 2006). Bronze vs. Gold stands out.
Zooming in to idle and lower power use, Bronze parts (S12, M12, Corsair HX) have idle power loss of 10 to 22W. Big gap between the 430W and the 520/620W. The 350-650W Golds stay within a ~5W spread at idle as well as over the 20-60W power range.
For high CPU utilization and gaming, Bronze vs. Gold is pretty clear cut. The average Bronze rated PSU uses 10W more at 100W output, 15W more @ 200W, and 25W @ 300W.
I may do a bit more chart-fu later on. Have fun discussing!