I am not sure, but I believe that you need to get the bike/trainer to “speak” to the laptop, not the Garmin.
I think a Ant+ speed sensor will do the trick for you.
You just get Zwift to read the speed sensor (you need a speed sensor or speed/cadence sensor on the rear wheel). You can then tell Zwift which trainer you have (it knows the load curve) and it will convert your speed to Watts. The Garmin doesn’t enter into the equation.
Works fairly well, the exception is that it’s worthless for sprinting (too laggy), which can be an issue in races.
You need a speed and cadence sensor. That communicates to the dongle, and Zwift (or TrainerRoad or any power-based app) uses that info to approximate power.
Because you have a Kinetic, you could also just get one of these Kinetic InRide 3 Sensor. It just plugs on to your trainer and transmits virtual watt data. Keep in mind that specific listing says ships in 2-3 weeks, but they’re also sold out on Kinetics website. The speed/cadence sensor is just as good an option though, and has the benefit of being usable outside as well.
Ohhh. So the speed and cadence sensor I currently have on my rear wheel that my garmin 520 speaks to should do it?
I know this sounds dumb but WHAT do I need to do to get it everything to speak together? Just get back on the bike on the trainer and start pedaling, and navigate through zwift set up or something? (just downloaded zwift to my MacBook and haven’t done anything yet).
Do you also have a power meter? If this is the case, you will have more accurate values. Otherwise, the speed sensor + trainer power curve will do the trick.
I used a KK Road Machine and virtual power on Zwift for nearly 2 years and found it very consistent and it turned out to be relatively accurate when I finally compared it to a power meter after I bought one. However consistency is the important thing and you’ve got the right trainer for that. It wanders much less than most with temperature so the remaining consideration is to be consistent with your setup. I always used the same tyre at the same pressure (I used 100psi), and the same amount of compression from the roller (I used 3 full turns from first contact). If you use different tyres, pressures and amounts of compression, the power required to achieve a given wheel speed may vary a fair amount but Zwift won’t know that.
It’s a very usable setup. I now use a Tacx Neo 2T and also have a power meter, but the experience is not massively different aside from the ability to simulate gradients. I do prefer my current setup though
one update - if you have a PC with Windows 10 then Zwift can do bluetooth to the sensor, no intermediate phone needed. Earlier versions of Windows needed the Zwift app on the phone to get to Windows with BT.
In your case you already have the ANT dongle so that’s probably a better route than bluetooth anyway…