The iPad Air, even with its lower capacity 32.4 watt-hour battery, lasts for almost a day when used as an LTE Personal Hotspot, according to tests performed by AnandTech.
The iPad 3, in comparison had a significantly larger 42.5 watt-hour battery, and lasted for almost the same time with the screen turned off and Personal Hotspot activated.
I set the iPad Air up as a personal hotspot, wirelessly tethering it to a 13-inch MacBook Pro with Retina Display. I started a constant 100KB/s transfer on the MacBook Pro (2x the transfer rate of my iPad 3 test) and with the iPad Air’s display off I measured battery life. Last time I chose 50KB/s as it was the average transfer rate across our old WiFi web browsing battery life test, I doubled the workload to be more reflective of more strenuous demands. In reality I’d expect to see a burstier usage profile, but that’s something for me to test down the road.
A total of 24.08 hours and over 8GB of transfers later, the iPad Air finally died.
How does the iPad Air, with the lower capacity battery, manage to last almost the same time as the iPad 3? The answer lies in the new A7 chip and the new Qualcomm LTE modem included in the iPad Air, both of which are built on a 28nm process as compared to the iPad 3’s 45nm process, which makes them a lot more power efficient.
So if you haven’t yet decided if you want a Cellular or Wi-Fi only iPad, you should consider this point as well when making the decision.