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I've seen the announcement of the new Raspberry 3 but didn't find any info regarding power consumption and heating.

A 1.2 Ghz 64-bit CPU is great but does it draw a lot more power? Shall heat be an issue with small cases with the Rpi3?

I've read that 2.5A are now needed but I've read contradictory infos on the subject: that 2.5A is only if you plan to run power-hungry USB devices.

So how much more power does this draw and is it a concern at all?

  • I believe the major power consumer on the Pi is the cheap DDR2 RAM, which probably operates at 2.5V (vs. 1.2 for the LPDDR style ram used in mobile devices such as phones); this is why the lower memory models consume less power even though they have the same processor. This test claims the Pi 2 processor maxed out on all cores only consumes 200 mA, meaning the RAM probably uses ~2x that. So the power consumption will be more, but probably not very significantly. – goldilocks Feb 29 '16 at 11:11
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    See also: raspberrypi.stackexchange.com/a/43235/5538 ...for some thoughts about the significance of PSU sizes and purposes. – goldilocks Feb 29 '16 at 11:36
  • I think the 2.5Amps figure is that it can now handle that much power for USB items - that has been an issue for most previous RPi models - that a standard USB is supposed to offer 0.5A supply but the previous ones could not - especially if there is more than one device wanting it. Heck, the very early B's had 0.14A polyfuses on each of it's two USB Ports... – SlySven Feb 29 '16 at 15:55
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    2.5 Amps is just a very high, safe figure -- it assumes the pi itself may use up to 1 Amp (which obviously it doesn't, if goobering's charts are correct) and the USB could use up to 1.2 Amps. However, considering what's on the market you might as well get a 2.5 Amp supply. 3 is obviously going to be overkill, but OTOH if you have a decent quality 2 A phone charger or powerback (which are common) that should be fine for all models. – goldilocks Mar 1 '16 at 7:12
  • "Shall heat be an issue with small cases with the Rpi3?" -> Of course not. Do you own a smartphone? How powerful is the processor in that? Additionally, it contains a lot more heat producing bits, and I do not notice phones with case mounted fans, 5g heat sinks, or even any ventilation of any kind. At best the (very minimized) case on a decent phone may get warm to the touch when working hard. The pi is not a supercomputer or a gaming machine. – goldilocks Mar 1 '16 at 7:47
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There's a short piece that includes Pi 3 benchmarks over at the PiMoroni blog.

All of the benchmarks below were carried out with just a USB keyboard and mouse connected with power supplied from the official Raspberry Pi Power Supply, with the exception of the WiFi dongle test in which the USB WiFi dongle was also connected. The Pis were naked, i.e. not in a Pibow, except for the onboard WiFi in Pibow test.

...

The benchmark we used here was Sysbench, computing primes up to 20,000. This is a heavily CPU bound test and, as such, ideal for comparing the [Pi Zero, Pi 2 and Pi 3] SoCs without side-effects from the memory or GPU.

...

Current was measured with an inline USB current and voltage meter. The built-in Wireless LAN and Bluetooth and the more powerful processor mean that the Raspberry Pi 3 draws about twice the current of its predecessor when under heavy CPU load (750mA vs 360mA).

Chart showing comparison of Pi current usage

Update

...and there's a second, similarly short, piece on Pi 3 benchmarks on the MagPi site:

You can’t get extra performance without a few sacrifices. The Pi 3 draws the most power of the test group, but its extra performance means it spends more time at idle. Those looking for maximum battery life should look at the Model A+ or the Pi Zero as an alternative.

Chart showing power consumption of various Pi models

  • 13
    Worth noting WRT tests like this that a task which theoretically can be done 10x faster on machine A vs. machine B will finish in 1/10 the time, so if processor usage is considered the only factor, then a Pi 3 could ideally be ~3x more energy efficient than a Pi Zero (775 / 225 = 3, 10/3 = 3). – goldilocks Feb 29 '16 at 13:14
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    From the data in the second chart I posted (which wasn't there at the time of @goldilocks comment) I'm less certain about energy efficiency savings. The idle current consumption on the Pi 3 looks to be much greater than that of the Pi Zero. – goobering Feb 29 '16 at 14:04
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    Again, not if at load the Pi 3 does work 5-10 faster than the zero. 0.58 / 0.25 = a factor of 2.32. Even using the conservative figure of 4x faster, 4 / 2.32 = 1.72. To turn that into a percentage, 1 / 1.72 = 0.58 means a Pi 3 will consume 58% of the energy of a Pi Zero to complete a multi-threadable or multi-process oriented task. The significance of the zero consuming 1/3 the energy while doing nothing I guess depends on what the purpose is, e.g., I use my B+ 24/7, not my 2, because what it's doing 80-90% of the time is very little. – goldilocks Mar 1 '16 at 7:02
  • @goobering: (and everyone) thanks a lot for your answer and graphs and links. – Cedric Martin Mar 1 '16 at 15:01
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    Interesting, the article I found here said the Pi3 consumes 2.5W at idle while the Pi2 did 3.2W... I'll have to try and find out myself (dont have a Pi2 to test though...) – Wilf Mar 3 '16 at 12:01
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When shutting down the HDMI and USB on the Pi3, the current drops to 160 milliAmps. In my tests, this was roughly 200 milliAmps on the Pi2. Thus, shutting down hardware (if you don't need it), can be a huge energy saver.

Update: Use this command to turn HDMI off: /opt/vc/bin/tvservice -o And this command to turn it on: /opt/vc/bin/tvservice -p

Use this command to turn USB off entirely: echo 0x0 > /sys/devices/platform/soc/3f980000.usb/buspower and this to turn it on: echo 0x1 > /sys/devices/platform/soc/3f980000.usb/buspower

Other measures which can greatly reduce power consumption:

  • Anything which uses the SD. So removing rsyslog might be useful.
  • A WiFi connection to a network. Althought I haven't been able to turn wifi off entirely, being connected to a WiFi network makes the Pi3 receive broadcast messages. This consumes more power than being just standby. So turn shut wifi down using ifdown wlan0 and turn it on using ifup wlan0 when you need it. Reduce even more power by not using DHCP every time you turn WiFi on.
  • Anything which makes the cores' frequency increase, by increasing the load.
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    I didn't know you could shut down the HDMI on the Pi - is that a setting via /boot/config.txt? – Dylan Pierce Aug 25 '16 at 1:23
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    Negative. Use this command to turn it off: /opt/vc/bin/tvservice -o And this command to turn it on: /opt/vc/bin/tvservice -p I googled "raspberry pi 3 turn off hdmi" and found this page: glframebuffer.wordpress.com/2013/08/28/… – Roel Baardman Aug 26 '16 at 8:03
  • Running the command to disable USB ports gives me this error (also with sudo): "-bash: /sys/devices/platform/soc/3f980000.usb/buspower: Permission denied" – glenneroo Aug 17 '18 at 22:05
  • according to /opt/vc/bin/tvservice --help the Pi 2 should know the same, -o brings the display off, however power consumption remains the same, then -p option doesn't bring the display back, any ideas? – tomasb Nov 14 '18 at 13:07
  • well -p option first turns the display off too for me so that partialy answers that turn back on problem – tomasb Nov 14 '18 at 13:16

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