Want low carbon footprint computing? Get a tablet computer

Sections: iPad, iPhone/iPod touch/iPad, Opinions and Editorials

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One of the laptop computer’s big advantages over its desktop counterparts has always been its relatively low power consumption. Even if you leave the power supply brick plugged in most of the time, as I’m inclined to do, the laptop’s generally lower power demands make it a lower carbon footprint device compared to most desktop models, although the advantage has shrunk somewhat since LCDs pretty mush replaced the old CRT technology across the board.

However, even a laptop is an energy-hog compared with touchscreen tablets. The Electric Power Research Institute (EPRI) recently assessed tablet computer power consumption, and calculates that users who charge their iPads every other day can expect to pay about $1.36 annually for the electricity needed to power the device, although the actual cost would vary in specific instances depending on local power rates. A typical laptop PCs will consume approximately 72.3 kWh of electricity each year at a cost of $8.31.


The EPRI analysis, conducted at its power utilization laboratory in Knoxville, Tenn., found that each model of the iPad consumes a miserly less than 12 kWh of electricity over the course of a year, based on a full charge every other day. For some context, a plasma 42 television consumes 358 kWh of electricity a year, and the Apple iPhone 3G consumes 2.2 kWh of electricity each year, which results in a power cost of $.25 annually.

Of course, the prodigious number of iPads Apple has sold, to say nothing of various other tablet computer brands and models, mean that these devices do still have a substantial carbon footprint. EPRI’s calculations show that the average energy used by all iPads at the time of the analysis was approximately 590 gigawatt hours (GWh). Were the number of iPads in use to triple over the next two years (a reasonable speculation), the energy required to power the fleet would be nearly equivalent to two 250-megawatt (MW) power plants operating at a 50 percent utilization rate. A quadrupling of sales in two years would require energy generated by three 250-MW power plants. Of course to some extent, that would be mitigated by tablet use displacing laptop and desktop computer use, conceivably even amounting to a net energy saving.

“As information technologies continue to change rapidly we see important implications for energy consumption,” said Mark McGranaghan, vice president of Power Delivery and Utilization at EPRI. “These results raise important questions about how the shifting reliance from desktop to laptop to mobile devices will change energy use and electricity requirements for the information age. At less than a penny per charge these findings bring new meaning to the adage, a penny for your thoughts.” Mr. McGranaghan also points out that changes in battery technology and technology features will affect energy requirements. “Our measurements indicate that the new Retina display iPads will consume about 65 percent more electricity per year than the first two versions did,” he noted, “What remains to be seen is how better batteries, better features and changing preferences will affect overall energy consumption by consumers as a whole.”

Of course, there are many other factors than just direct energy consumption that contribute to a device’s overall environmental footprint. While the iPad is a commendably parsimonious user of electric power, it has a number of serious environmental shortcomings, the most glaring of which is its being to a considerable degree a hermetically sealed disposable device, since changing its battery, which has a finite and relatively short lifespan. After the warranty expires, replacing the battery requires shipping the iPad back to Apple, which will charge you $99.00 plus $6.95 handling, which, given the rapid obsolescence of these machines, would be a questionable value. Google’s new Nexus 7 tablet, by contrast, has a user-replaceable battery. iFixIt gave the Nexus 7 a Repairability Score of 7 out of 10 (10 is easiest to repair), noting that the rear case is very easy to open, and requires minimal prying effort with a plastic opening tool to remove, all fasteners inside are standard Phillips #00 screws, battery replacement can be executed without soldering (or even a screwdriver), and that many components—including the I/O ports—can be replaced independently of the motherboard.

By contrast, iFixIt awarded the iPad 2 and New iPad a shameful 2 out of 10 Repairability Score, observing that the iPad is very difficult to disassemble with the front panel glued to the rest of the device, greatly increasing the chances of cracking the glass when trying to remove it. Inside “gobs, gobs, and gobs” of adhesive hold down everything in place, including the prone-to-start-a-fire-if-punctured battery.

The iPad is admirably easy on electricity, but Apple really ought to do a lot better in the repairability and recyclability departments.

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