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I am considering buying a Thunderbolt to Gigabit adapter to save my MBA power consumption as I can shutdown the Wifi, assume it use a lot of power.

Anyone tried before and it works? How many % of power can be saved? e.g. increase the battery life by how many %?

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  • Since there are several generations of MacBook Air you won't get a good answer unless you specify which CPU / model you wish to compare.
    – bmike
    Jun 22 '13 at 18:04
  • @bmike, 2001 Mac Book Air.
    – Yoga
    Jun 25 '13 at 15:38
  • "e.g. increase the battery life by how many %?" makes no sense. And if you're going to be plugged into an ethernet cable anyway, why not just use WiFi + your MacBook's charger? It's wasteful to constantly wear down your battery when an outlet is available.
    – Alexander
    Jul 15 '13 at 23:48
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I have no precise data; however, I do have a MacBook Air mid 2012 and I had to buy a Thunderbolt Gigabit adapter. What I can say is that it consumer substantially more than the WiFi chip. Fully charged, I can reach 5+ hours using the WiFi chip; when the Thunderbolt Gigabit adapter, it's enough if I get to 3.5 hours.

Honestly, this was an authentic shock to me, and I blamed the battery at first, thinking it was faulty and needed to be changed; however, using the WiFi, battery life gets back to 5+ hours, so I'm pretty sure this has to do with the Thunderbolt Gigabit adapter.

This is not a scientific test, but on average I use the Mac to surf on the internet, normal stuff. Anyway, I got this decrease in performance without changing my usage pattern.

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I am using on a daily basis a MBA2013 Haswell, and I can confirm that the thunderbolt ethernet consumes much more power than the WiFi link. I can get up to 12 hours on wifi, never had more than 7 on ethernet.

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My guess is you will see little to no power savings by shifting the network from the wireless interface to a thunderbolt interface. In fact, the power consumption of running thunderbolt and the chipset in the adapter might be higher than the wifi chipset, so this may be an interesting test should someone perform it.

You will find that disabling the network is what yields the primary power savings on 2012 and older MacBook Air (and Pro) since the network delivers interrupts that prevent the CPU from sleeping and let the machine do more work.

If you change your habits and reduce CPU load, screen brightness and disable network access to let an Air work locally, you will extend your battery life from 2x to 4x in my experience on the 2012 and older Air.

The 2013 Air are not out for long, so it's a guess if the effects there will be more or less. My guess is that network access will reduce life there even more (since they are designed to be even lower power at idle than the previous generation), but it remains to be seen in practice.

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  • Yes, I am using 2001 Mac Book Air. When disabled the wifi, I see vital power saving..
    – Yoga
    Jun 25 '13 at 15:39
  • I assume a 2010 Air? I don't disagree with turning off the network saves signifiant power - but my measurements have been that the thunderbolt network doesn't save significant power over wireless network assuming you only are using one or the other.
    – bmike
    Jun 25 '13 at 15:45
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I'm on a 15' rMBP 2014 and whenever I use the adapter (thunderbolt to ethernet) I notice a double rate of battery's charge decrease. If I use wi-fi, I leave the office with 50% charge whereas with the adapter I leave with 15% or less. Of course I always start with 100% charge and performing pretty much the same tasks every day.

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Exactly the same experience here. Significantly less time running from the Thunderbolt to Gigabyte Ethernet adapter.

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