You searched for: “effective radiated power
effective radiated power, ERP (s) (noun), effective radiated powers (pl)
A measurement of the output of RFID reader antennas used in Europe and elsewhere: An effective radiated power is the same as "equivalent radiated power" and is an IFEE standardized meaning of directional radio frequency power.

ERP is usually expressed in watts and is not the same as EIRP.