Smartphone energy management – at last there is an app for that!


The World Bank issued a report yesterday showing that the number of mobile phone subscriptions in use worldwide, both pre-paid and post-paid, has now reached over 6 billion.

The report went on to reveal that more than 30 billion mobile applications, or “apps,” were downloaded in 2011 alone – these apps extend the capabilities of phones, for instance to become mobile wallets, navigational aids or price comparison tools. However the apps also have a cost associated with their use – they drain the phone’s battery.

Carat - smartphone energy managament

Some of these apps are energy hogs – they require a lot of energy to run, and so they drain the phone’s battery quickly (maybe they are legitimately using the camera, the GPS radio, and the 3G network simultaneously). Other apps have bugs in them whereby they may not properly close out battery use after a particular function and they continue to drain the battery. Until now, there has been no way to identify which apps were the ones draining your battery’s charge.

I have written a couple of times here before wondering why there was no energy management app for smart phones. Now there is – Carat.

Carat has been developed by a very small team at the Algorithms, Machines, and People Laboratory (AMP Lab) in the Electrical Engineering and Computer Sciences (EECS) Department at UC Berkeley, in collaboration with the Department of Computer Science at the University of Helsinki.

The app is free and available for both the iOS and Android platforms. And the client-side code has been uploaded to Github, where anyone can download it, and if they have the development chops, potentially fix any issues they find, or even improve on the app.

As every Smartphone owner knows, battery life is a massive problem. Carat discovered just how big a problem when TechCrunch wrote a piece about the app a few weeks ago. Carat had estimated that they’d pick up an extra 10,000 users as a result of the article. Instead 250,000 people installed the app on their phones and Carat had to scramble to deal with the massive, influx of data.

As can be seen from the image above, Carat gives you advice on ways to get longer life from the battery in your smartphone by identifying Battery Hogs (apps that use a lot of energy), apps with energy bugs and advising on how much extra battery life you will save by re-starting or killing the app.

Carat also reports your J-Score:
Carat J-Score

The J-Score is “the percentile battery life you see relative to all other devices being measured by Carat”, so the J-Score of 54 reported for my phone means my expected battery life is better than 54% of Carat’s users.

One thing to be aware of is that because Carat needs a certain threshold of application usage before it can report accurately on your apps, it typically takes a weeks usage before it starts advising you on how to get better battery life for your device.

Speaking to Carat developer Adam Oliner last week he informed me that some of the next steps for the app will be to publish api’s so that app developers will have better access to the energy consumption info of their applications.

What is interesting about this app is that it was developed as a research project, and not by one of the Smartphone Endpoint Management providers. You’d have thought saving their customers money and reducing their emissions (through using less energy), while keeping their employees more productive (by prolonging the battery life of their smartphones) would have been a no-brainer.

Perhaps, now that it has been shown that this is possible, we’ll see more of these types of apps emerge.

Image credit Tom Raftery


Forget mobile phone chargers – they are not the problem!

I participated in the recent IBM Global Eco Jam and there were some fantastic discussions there.

One of the discussions surprised me though – people were still talking about unplugging mobile phone chargers as if that was a significant problem. It is not. On the contrary, it is a dangerous distraction.

Watch the video above. Seriously, do. I’ll wait.

The mobile phone chargers I tested all consumed 0.1W or less of electricity when left plugged in and not charging a phone. That is minute.

Sure, I get that if you add up all the millions of mobile phone chargers across the country, all those millions of 0.1W adds up to a significant load. I get that. I do.

LED Light

LED spot light

However, if you change one 50W halogen bulb for a 3.6W LED alternative that is the equivalent of unplugging over 460 mobile phone chargers. And that’s just from changing one bulb. How many bulbs do you have in your house? How many houses are there across the country containing how many bulbs?

Or forget light bulbs. What about the electricity draw of other devices in your house when they are plugged in but not operating (this is called standby power!)?

Well, my microwave consumes 3.5W when plugged in and not in use (that’s 35 mobile phone chargers worth), my printer draws 5.9W when on and not actually printing (59 mobile phone chargers worth), my Nintendo Wii draws a whopping 9.5W when on and not in use (95 mobile phone chargers worth), even cradles for cordless home phones can be consuming eight times more electricity than mobile phone chargers!

Mobile phone chargers, for some reason, seem to have been picked up by people as the bad boys when it comes to standby power. That is a dangerous fallacy. Why dangerous? People who are trying to do the right thing are ensuring that they unplug their mobile phone chargers, potentially unaware that their microwave/printer/games console is consuming orders of magnitude more power than the phone charger.

Switchable power strip

Switchable power strip

Don’t get me wrong, sure you shouldn’t leave your phone charger plugged in, but it is likely that there are far larger standby draws in your home or office you should be aware of. Educate yourself. Find out which of your devices draws the most power

How do you know which devices consume the most power? Find a little plug-in electricity meter to measure the power draw of your appliances, they are quite cheap and easy to find online – check here, here and here, for example. In some cases your local utility company may even supply them.

One of the things I do is to plug multiple devices into a power strip with a switch, this way I can quickly kill their power draw by flipping a single switch.

But stop talking about unplugging mobile phone chargers – by themselves they are a minuscule draw. Unplug everything.


Mobile phones – distributed air quality sensor network?

Since giving my talk on sustainability in the mobile phone sector at Mobile 2.0 in Barcelona a few weeks back and writing my post about how Augmented Reality on mobiles could be transformative for Green tech I have been thinking a lot about how mobiles could make a significant positive contribution to the planet.

The context behind this is that while there are 1 billion PCs in the world and 1.4 billion internet users, there are 4 billion mobile phone subscriptions and climbing. One possibility I posited at Mobile 2.0 was that mobiles could become clients for grid computing projects like IBM’s World Community Grid. This would add significantly to the compute power of the grid (but for now battery life considerations probably means this is still a few years out).

The other thought rattling around in my head was probably sparked off by my discussions with IBM execs around their Smarter Planet initiative. It occurs to me that if mobile phones had built-in air quality monitors, you could very quickly build up a real-time map of pollution hotspots. Current municipal pollution monitors are static and far too few in number to give a meaningful picture of air quality but if mobile phones had this capability, the combining of the air quality information with the GPS data from the phone would allow for pinpointing of pollution trouble spots very quickly.

Obviously for this to be effective, the data would need to be anonymized and uploaded to a central server. Also, the pollution information would need to be made freely available for everyone’s consumption. There may even be a business model there for someone to pay mobile phone users to sample air and upload the information.

A quick bit of research around this thought and I found the video above showing that not alone is it feasible but it wasn’t a hugely original idea on my part 😉

With the recent news of urban pollution being responsible for lower IQ in children and being implicated in premature births of infants and preeclampsia, there is a definite health imperative for something like this. Especially in China, where air pollution is causing massive health problems. Imagine if the Chinese authorities mandated this the way they mandated that all mobile phone chargers use usb back in 2006! Very quickly economies of scale would drive costs down and competition amongst manufacturers would mean smaller chipsets to do this.

Original Rockwell GPS receiver - image from

Original Rockwell GPS receiver - image from

For anyone who thinks that air quality monitors would be too bulky for mobile phones, just have a look at what the original GPS receivers looked like (large backpacks) and now they are embedded in most smart phones!

One final thought harking back to my post on Augmented Reality, with air quality data from mobile phones uploaded to the cloud (unintentional pun, sorry!) it would be very straightforward to create an Augmented Reality view of air quality allowing mobile phone owners to ‘see’ pollution in their immediate environment – imagine how quickly that would drive home to people the seriousness of their air quality situation.