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Everyone is saying that Wi-Fi is more power-efficient than 3G on smartphones.

But, I don't think so, because two radios are turned on at the same time, the 3G radio is still active when enabling Wi-Fi

There is some reliable proof to support this?

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  • 2
    Please add a few links for someone making the claim :)
    – nico
    Apr 4, 2013 at 16:31
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    You don't HAVE to have your 3G turned on when WiFi is on. Obviously having both on is going to drain more power than WiFi alone.
    – DJClayworth
    Apr 4, 2013 at 16:58
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    @DJClayworth: certain phones (mine for sure) turn off the 3G when they get a WiFi signal
    – nico
    Apr 4, 2013 at 17:29
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    @DJClayworth: well, oversimplifying a bit, 3G is just 2G + 3G data connection. For normal voice call you just use 2G GSM.
    – vartec
    Apr 4, 2013 at 18:28
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    The issue isn't dominated by the connection method when the connection is idle. It is the transmission of data that matters. On WiFi most non-voice data will go WiFi: the question that matters is whether transmitting that same data via 3G would use more power. "Power efficiency" is ambiguous if you don't define what the power is being used to do. A better question would be "which uses more power to transmit, say, 1MB of data?"
    – matt_black
    Apr 4, 2013 at 20:26

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Yes, WiFi is significantly more efficient, as the protocol is completely different. Once association with access point is established, WiFi only uses energy for actual transmission of data. On the other hand 3G remains in high-power state even after transmission is done.

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source: "Energy Consumption in Mobile Phones: A Measurement Study and Implications for Network Applications" Niranjan Balasubramanian, Aruna Balasubramanian, Arun Venkataramani, Department of Computer Science, University of Massachusetts Amherst

It's also worth mentioning, that WiFi has legal limit of power output of 200mW (0.2W), while 3G devices legal power limit is 2W.

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  • I think the UMass Amherst link and graph provides the right answer. Most people notice that their battery drains faster with Wi-Fi enabled just because both radios are still on. My Verizon 4G phone drains really fast when I'm in 4G range even without WiFi enabled. With WiFi turned off and in 3G only range, I have the longest standby time. Another reason NOT to use WiFi when you are away from home or office is security. You do not want your phone wandering into any random WiFi networks that may be setup to do harm to your data. I turn off my WiFi radio when I leave the house or office for secur
    – mdSeuss
    Apr 4, 2013 at 16:50
  • The reason for WiFI being more efficient in transferring data is not that it switches to a low power mode faster than a 3G connection does after transmission. That fact only speaks to tower search being very expensive.
    – bobobobo
    Apr 4, 2013 at 20:24
  • @bobobobo: you're going into details why it stays in high-power state
    – vartec
    Apr 5, 2013 at 8:41

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