Two Raspberry Pi A+ arrived from Farnell yesterday, so I spent the afternoon doing some power measurements. I also made a comparison video showing power measurements for an A+, a B+ and an old model A Pi.
I wanted to see how much current each Pi would consume under four circumstances….
- Idling in command line – low CPU load
- Starting LXDE desktop – heavy CPU load
- Watching Big Buck Bunny in HD – GPU load
- Filming Full HD video with Pi camera – GPU load + camera load
So this was done for each Pi in turn, A+, then B+, then A. I didn’t bother with the B as we had a separate B+/B comparison when B+ was launched. (I did the B rev 2 without filming the next day and updated the table.) All measurements were using a bench-supply set to a regulated 5.2V.
Video Of The Testing
Here’s a video of the testing. I used two cameras to get a close-up view of the meter readings. (Always try new things.)
What About The Results?
Clive Beale made a graph of the results which, obviously, I wish I’d thought of doing. It shows the comparison very nicely…
— Clive Beale (@clivebeale) November 13, 2014
Idling CLI (0.52 W)
Idling in the command line, the A+ uses 100 mA, which is 40 mA less than the A, half the current draw of the B+ and a bit over a quarter of the original model B (360 mA).
Idling, the A+ uses 71% of the power of the model A.
CPU Load (0.68 W)
Loading LXDE, the A+ uses 68% of the power of the model A.
GPU Load (0.73 W)
Under GPU load, the A+ uses 70% of the power of the model A.
GPU Load + Camera (1.2 W)
Under GPU + camera load, the A+ uses 72% of the power of the model A.
Obviously these figures are subject to a small amount of experimental error, but I think we can safely say that the A+ uses about 70% of the power of a model A. That’s a very useful improvement. Brilliant for battery powered applications.
Depending on what you’re doing, the A+ uses between 50% and 70% of the power used by a B+ (the camera adds 100 mA to both, which affects the A+ proportionately more in % terms).