I found this post: Tsw202 PoE power consumption via cli but unfortunately it was never resolved. I am trying to read out the PoE power usage via CLI but I seem unable to do so.
Of course, as soon as I asked this I worked it out.
There is an interesting item in the list poeman. You can interrogate the items in the list using ubus -v list poeman. From this, I found that there is a method dump. Therefore, running ubus call poeman dump gives the useful data:
For most stable way between versions it is recommended to use API. So via CLI it would be api get /ports_settings/status or api get /ports_settings/status/{port id} for any specific port. poe_enable - is poe enabled, power - is poe being used, budget - current in mA