I am currently traveling for work, so cannot take the measurements. From my memory, I believe that the total power on transmit (CW) was approximately 1.9 amps at 13.8 vdc = 26.2 watts. SSB would vary based on the audio. Regardless, I believe that the 15 watt estimate is low. I would use 25 watts. This can be adjusted by the setting of RV1, transmitter drive.
Also from memory, there was a lot of worry back when the group was working on smoothing the power across the bands that the efficiency of the transmitter was on the order of 40%, relatively low. Assuming the 10 watt output, 40% would be at least 25 watts in. This also coincides with the current measurements from memory.
Am getting old, so memory might be faulty. Would suggest someone actually measure their rig for validation.