Port PoE usage is reported as Watt-hours consumed over the timespan specified when making the call.
So if you want average power usage over period T, set the timespan to T and normalise to Watts by Wh/T (with T in hours).
Note that this call doesn't use a t1 parameter, so whether you use t0 or timespan it will always return data looking back from the time of the call. I just run it daily at the same time to build up long term stats.
Afaik switch PoE budgets still aren't visible, but it's simple enough to use a look-up table, just need to remember to add new switches to the table when they are released.