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Comment by recursive | Hacker News Reader

It seems odd to me to leave wifi turned on if I'm not planning on using it. I keep all my phone services off unless I'm using them for something. In my imagination, this prolongs the hilariously short battery life of modern smart phones.

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If you are setup to automatically connect to known Wi-Fi networks, and you often times are able to, it can actually result in large battery savings.

Transferring data over Wi-Fi is more efficient than going over a cell network. With how many network services exist on phones now days, your phone can spend a lot of time doing network transmissions. Wi-Fi is more efficient for this, thus the savings.

You can see this in good cell phone reviews, they'll have a battery life test for Wi-Fi web browsing and another one for 4G web browsing, the Wi-Fi test will demonstrate a much better battery life.

Another way to think about it, is if you are in an office building that doesn't have cellular antennas places throughout it, then to connect to the cell network your signal has to get through the building material. If there is Wi-Fi available, odds are those antennas are close by and easily reached.

(Of course really noisy Wi-Fi environments can change the math on all this, but I do not know by how much.)

how much of an improvement are we talking about?

Naturally, it's even cheaper on battery life to turn off both data AND wifi, leaving your device not connecting to anything.

Why use a smartphone then just get a normal phone will last a wrek

It is a question of cognitive load. If you turn wifi off and on you need to _remember_ to turn it on when you are in an "I want to use wifi" zone. If you forget then you end up using your data plan.

You could use a geofencing app to handle turning wifi on/off (say at home and work, etc) but then you are just trading battery issues.

Additionally, at least on android, wifi scanning improves location services. At least for me those are important, specifically when I am not at home or the office.

In my experience, being connected to solid wifi will drastically increase your battery life vs. the phone trying to use the cell network for everything, especially if your cell service is noticeably worse than the wifi.

> especially if your cell service is noticeably worse than the wifi.

I’m not sure if that case exists anywhere in the civilized world. Subways and trains all have 3G networks, buildings have them, even in rural areas every 3rd tree you pass is a hidden 3G tower.

I don’t think I’ve seen a place without 3G anywhere in Germany in my lifetime (but I’m only 20)

Come to Chicago. In the lobby of my building (granted 40 floors of concrete) I can get any of no signal, 2g, 3g, or LTE - in the same spot minutes apart.

In more hilly/mountainous areas (like Connecticut or upstate NY or even parts of Pennsylvania) cell service kind of stinks. I've been to plenty of places where I get no service, even outside.

I don't have 3G at work. I work in an office building <100 miles from silicon valley.

A use case for keeping it on is that WiFi can be used to improve your phone's location accuracy ("GPS" services): https://en.m.wikipedia.org/wiki/Wi-Fi_positioning_system

It also significantly reduces the time to get a location, where satellites can take minutes to acquire (at least that was the case, back when I worked with GPS at that level)

If you are on the Project Fi network, Google can use open wifi networks for making calls. You'd need to leave wifi on to take advantage of this.

This is taken care of by google, so I never connect to a network/sign-in, etc.

Can you remember any places or networks where you connected to open WiFi for calling? I'm in the Bay Area and have had Fi for about 6 months, but I can't remember ever seeing this (despite advertised claims).

Edit: To be clear I'm not questioning your statement. Just curious to hear where Fi takes advantage of this.

Two places that I know for sure: 1. Planet Granite in Sunnyvale. 2. Great Mall in Milpitas.

There are several other places where it doesn't use the network unless I explicitly select it though (eg most Philz coffee locations, my work, etc)

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