I live in area vulnerable to power outages, so I use UPS to power my hap ac2. My goal is to minimize Mikrotik’s power consumption, even if I’ll get 5 more minutes of battery life.
When electricity switches off - hap ac2 enables wifi hotspot (tx-power=5), so I’ll be able to get some wireless internet while mobile network is not available during blackouts.
The question is - as I don’t care about speeds and wireless coverage, what consumes less power for 2-3 clients - 2.4ghz or 5ghz wireless ?
On hAP ac2? I’d say it only depends on Tx power setting. Both radios are run by same wireless chip inside same SoC.
Due to lower free.air loss in lower frequencies I’d expect slightly better coverage of 2.4GHz radio, so you might be able to reduce Tx power slighly and still get same coverage. By all means set up wifi to only use 20MHz channel, this way transmitted power will be spread over narrower bandwidth, offering better coverage (again).
Oversll you might be able to reduce Tx power by 10 dB (from, say 25dBm to 15dBm, which translates to reduction from 300mW to 30mW). If your baseline Tx power is 5dBm, then reduction from 3mW to sub-mW won’t save you much.