Zpower way low

My virtual power shown on Zwift (is it called Zpower?) is consistently 30%-50% below my virtual power shown at the same time on TrainerRoad (which, to be fair, is 5-10% above actual power as read by PowerTap. I don’t usually use my race wheel with PowerTap on the trainer, which btw is Kurt Kinetic Road Machine)

I know virtual power is just a number, but still.  I wonder if anyone else has experienced this and if there’s anything to do about it.

While comparing Zwift to Trainer Road isn’t an apples to apples comparison, a significant difference between Zwift and a PowerTap is concerning.

If you verify there is that much of a difference between the PowerTap and your Zwift readings, check to make sure your setup meets our zPower guidelines as your wattage will be different if anything doesn’t match. The KK trainers are some of the most accurate zPower curves, so they should be very close to a power meter.

Let us know if you need more help investigating.

I started on Zpower because I couldn’t afford a power meter at the time. When I added a power meter, I found I had lost roughly 35 watts (for me 0.5 w/kg). So Zpower was too high. I also use the Kurt Kinetic trainer. It was at times even higher when I used an aero bladed wheel instead of a standard wheel (the computer signal is only wheel revolutions. It estimates power based on normal (32 round spokes) not aero (18 bladed spokes). That gained about 10 watts or so. (great for outside).

There are many variables, of course. I would expect many riders to have 5-10% higher numbers on trainer compared to outdoor roads. It seems the real problem is TR.

I found an ant+ Powertap wheel on Ebay and I love it. Best bargain on used power meters. I got it especially for the Academy. And nothing rides like the Kinetic.