Raspberry Pi 3 : Is it worth for energy efficiency ?

Olivier Philippot

The Raspberry Pi 3 is out. This is good news for Pi lovers, because #3 brings more features and more performance. But energy is important if you want to use it on battery. How about its energy efficiency?

The folks at RaspberryPi.org did their homework, and they released a handful of benchmarks to show how much performance has improved.

CPU consumption

They also benchmarked the energy aspect, and indeed, this shows an increase in power draw:

Power consumption

Before we go on, let me praise RaspberryPi.org people for releasing this benchmark: how many hardware makers have such a transparency level about energy consumption? Great job folks, well done. Now let’s put our Green IT glasses on, and look closer at these metrics. You may wonder if the performance gain of the Pi 3 is worth the extra energy consumption? To answer this question, we need to derive another metric from these: performance over energy. Performance by watt is for example a widespread metric on HPC servers. The RaspberryPi.org benchmarks have two different performance indicators: MIPS and MWIPS (respectively from Dhrystone and Whetstone benchmarks). On the energy side, they chose to use Amperes (A), which show the intensity of electrical power. Ah or Wh would have been better because they represent the energy consumption (which is power over time), and not an instantaneous value such as power or current. Anyway, let’s do with what we have, and check the MIPS/A or MWIPS/A ratios, as indicators of power efficiency.

Charts

The Pi 3 is somewhat better for floating performance efficiency (MWIPS/A) but it’s a tie for integer performance efficiency (MIPS/A). If you look at the power in idle mode, Pi 3 is 3 times more consuming that the Model A+ and the Zero. So Pi3 is not your best choice if you want an energy efficient solution, which is confirmed by RaspeberryPi themselves: “Those looking for maximum battery life should look at the Model A+ or the Pi Zero as an alternative.”. Fully agreed: if the Model A+ or Zero are powerful enough for you, you can stay with these and get a longer battery life.


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