I think MySensors do not support this P1 power meter.
For S_POWER type you have got only this variables: V_WATT, V_KWH, V_VAR, V_VA, V_POWER_FACTOR
If you need this two tariff power meter in Domoticz you must use other platform ( ESPeasy for example ) witch support sending JSON http calls.
For P1 power meter format is:
IDX = id of your device (This number can be found in the devices tab in the column "IDX")
USAGE1= energy usage meter tariff 1, This is an incrementing counter
USAGE2= energy usage meter tariff 2, This is an incrementing counter
RETURN1= energy return meter tariff 1, This is an incrementing counter
RETURN2= energy return meter tariff 2, This is an incrementing counter
CONS= actual usage power (Watt)
PROD= actual return power (Watt)
USAGE and RETURN are counters (they should only count up).
For USAGE and RETURN supply the data in total Wh with no decimal point.
(So if your meter displays f.i. USAGE1= 523,66 KWh you need to send 523660)