Calculating efficiency of transmitter

How can I calculate the efficiency of a transmitter?
I would like to know if my thinking is correct by a simple example:

Assumming that a transmitter outputs 4W of RF power at 50R and consumes 290mA at 22V.
Then for 4W output, the transmitter consumes P= 22v * 0.290A = 6.38W

So, at 6.38W of consumtion, 4W is outputed.
bringing that to % percentage, it is (100*4)/6.88 = 62.69

This means that the transmitter is 62.69% efficient.
Am I right?
    
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Yes, you are right. If the 4W is the peak power, then the number is peak efficiency. If 4W is average power, then the number you have got is average efficiency.