A growing use of beacons is for continually monitoring using sensor beacons. However, one concern is how continually reading a Bluetooth sensor beacon might affect phone battery life.
There’s a recent research paper by Kleomenis Katevas, Hamed Haddadi and Laurissa Tokarchuk of Queen Mary University of London, UK on Power use : SensingKit: Evaluating the Sensor Power Consumption in iOS devices. It looks into Bluetooth beacon (phone) power use and, as a baseline, compares this to phone battery power use by sensors in the phone. They evaluated beacon broadcasting and scanning modes separately and together.
Very few scenarios use the phone to broadcast so the pink dotted line probably has less relevance. Looking at the scanning test it can be seen that it consumes power of the same order of magnitude as other sensors in the phone itself. Bluetooth LE scanning isn’t especially power hungry. Nevertheless, the 25hrs hours operation time on battery might be a limitation for most sensing scenarios.
An omission in these tests is that they only considered scanning rather than connecting. Some beacons need to be connected to via Bluetooth GATT, to obtain sensor data, that uses more phone battery power because it requires the phone to transmit to the beacon instead of just listening to the advertising scan data.
In practice, sensing projects are often better served by using a WiFi gateway or a phone/tablet permanently plugged in rather than a user’s battery-powered phone. This allows the device receiving sensor data to be mains powered removing concerns regarding device power use.