Power difference between trainer and power meter

I have an Elite Direto and a Stages power meter. I’ve been using the Direto for power and the Stages just for cadence. My question is this, is my FTP lower using the Direto than it would be using the Stages due to where the power is measured. Basically at my cassette vs. at my crank arm? I’m using the Direto for power because it’s been tested to be very accurate by DC Rainmaker and GP Lama. And when I started my current TR program, that’s how I had it set and don’t want to change it halfway through my winter training. Thanks

Theoretically the Direto should measure lower power than the Stages, but honestly there is no way to know without experimenting. Many people have reported their trainer measuring power high, and many have reported their crank/pedal-based PM reading low. If you plan on using your bike outside eventually, I would recommend using the Stages for power so that you can compare inside/outside rides. If you’re concerned about switching in the middle of winter training, record the power reported from both the Direto and the Stages when you do your next ramp test. That way, you can estimate what your FTP would have been if you had kept using the Direto (manually take 75% of the highest 60s power) while still getting a new FTP value for use with the Stages. You can do this by connecting your head unit to the Direto over ANT+ and recording the ramp test while simultaneously using power match + Stages with TR.

Madman2. Thanks for the advice. I will give that a shot on the next test.