AC will behave similarly to that of N, correct?
No. As I said, first of all an additional modulation scheme for extra-short-range is introduced. (Realistic usefulness is extremely limited due to the extreme SNR requirement)
Furthermore, without that modulation scheme its only comparable if you're running your current N network in 5GHz mode.
This is not the norm.
And the reason I state 'reduced range', is because it means that the SNR quickly reduces over range. With a lower SNR, the system is forced to use a modulation scheme with fewer bits per signal. (Lower effective throughput)
It'll quickly drop from 256-QAM to 64-QAM, and over a much lower distance drop from 64-QAM to 16-QAM. Your throughput speed is now considerably slower.
That is to say, the 64QAM range of standard N might be 5~ meters indoors. For AC (or 5GHz N), the range of 64-QAM could be just 2-3 meters, and less than 1 meter for 256-QAM. That 1 meter range is the only range where speed would actually improve with AC. It would be identical to 5GHz N at all other ranges, and worse than 2.4GHz N beyond 2-3 meters.
(Note: I'm being somewhat harsh with the ranges here, you're best to test N yourself)
Though there is one exception, AC permits bandwidths in excess of 40 of N, up to 160. That would give theoretical improvements that are still ~4x over 5GHz N. But the question is how viable running with that bandwidth is. In addition theres the question whether the card even supports this bandwidth.
As for power, the concern is less on the access point -and more on the (portable) device. AC speeds heavily emphasize MIMO - and the downside of MIMO is that you multiply the number of antennas. This means that such rigs require significantly more space, and many times more power.
Also keep in mind there are legal limitations on signal power output. And to my knowledge, that limit is already the norm.
If you want improved wi-fi speeds on iOS devices - I suggest you push for Apple to actually make proper use of the N standard first. As is, it doesn't handle Short GI or 40MHz bandwidth resulting in a max throughput of 65mbps rather than 72 (or 150 for 40MHz bandwidths). In addition, its inability to handle MISO means its less capable of error detection and correction (means it has to downgrade its modulation earlier).
