I agree with colleague Adrian Kingsley-Hughes that the big story of the new iPad, more than the Retina Display and inclusion of LTE, is the battery improvement. Apple doesn't play games with its claims of product battery life, and if it says 9 hours of operation using LTE that's probably accurate. That run time is a significant achievement for operation using battery-guzzling LTE technology. What's not clear about Apple's claims is why the same battery in the Wi-Fi only iPad only produces only 10 hours of runtime.
The 42.5 watt-hour battery mentioned in the official iPad specifications above is a big honking battery for such a thin and light tablet. It's clear the same battery is being used in both the Wi-Fi and Wi-Fi + 4G models, as indicated in the two columns of the specs above.
The 10 hours of the Wi-Fi only iPad is in line with the run time of the current iPad 2, which is no surprise. What is a surprise is why there is only a one hour run time difference indicated by Apple for Wi-Fi and LTE operation. I have tested LTE operation on at least a dozen smartphones and two tablets, and the 4G technology has used significantly greater power than Wi-Fi in every case.
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In my extended testing using LTE on a 10.1-inch tablet, the battery drain compared to Wi-Fi operation was noticeably faster, at a rate of nearly 2-to-1. The tablet would run 10 hours on Wi-Fi, and perhaps 5 hours on LTE connectivity.
My experience with LTE proves how significant the 9 hours of run time that Apple is providing with the new iPad. This is a tremendous achievement, and probably the most significant improvement over the iPad 2. This upgrade makes it all the more confusing why Wi-Fi operation isn't better than older models of the iPad. I would expect a near doubling of run time on Wi-Fi over LTE, even with the Retina Display.
Either Apple has implemented a totally new LTE radio that is very battery friendly, the Wi-Fi only iPad has a different battery than the 4G model, or there is some other mysterious difference present in the two models. I can't wait for the standard breakdown of the new iPad models once shipping to see what is going on inside the slate.