Power in zwift vs. TR

Been zwifting to do my HVLIT and put in big hours. Started a plan this week to prep for a XCO race in 19 weeks.
After one session I noticed holding the same power target on TR vs Zwift is SIGNIFICANTLY harder. Did a 3x12@239 for my first workout and it was pretty hard. I’ve done 233 for 66 minutes on Zwift. What gives?
I’m using an elite suito smart trainer and calibrate nearly every ride.

are you using an ERG workout in Zwift? If not, you’re in sim mode. Perhaps you’re feeling negative gradients?

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I have all that turned off. Same resistance regardless of gradient

have all what turned off? how have you configured it?

I’m riding right now lol
Just want to clarify this isn’t necessarily a problem. It’s just weird and I’m curious

I found holding power harder in Zwift than TrainerRoad. Both have slightly different responses. It took me a few rides to get use to both.

Same power meter / same trainer.

Note* I don’t use erg mod.

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We have seen comments over the years, that TR does a better job of handling power in general, but especially in ERG mode when compared to Z. That may be the entire difference.

For clarity, what exactly (app and such) and when exactly (before or after any warmup) are you calibrating your trainer?


Was contemplating this for some reason….

I think there are a couple things that could be at play.

  1. Too frequent and inconsistent calibration: are you always calibrating with the same method (zwift, TR, elite app)? Maybe a rogue calibration was in play when you did the 66min?

  2. Difference in ERG vs Resistance: if your cadence is erratic you could be getting “corrected” by TR and thus doing more work than if your cadence and power were more steady

  3. You aren’t as fit as you think you are? Don’t really say when the 66min effort was in relation to the workout

  4. Fueling and overall nutrition and rest: poor sleep, poor eating can lead to poor performance

  5. Watts are watts: maybe your motivation is lower for blue bars than fake scenery in which case HTFU


There’s some oddity with trainer difficulty. I haven’t kept up with it, but GPLama has done a deep dive on it.

If you remove controllable trainer, and set the resistance with a separate app, it might be a better comparison. Apples to apples, so to say. The same with TrainerRoad, if you can pair it as a power meter only (not sure if you can), but if not, set it to the same resistance level, say 15% for both Zwift and TrainerRoad, and “free ride” your workouts, using your gears.

AFAIK, as long as you pair it as a controllable trainer, it’s in SIM mode.

As Chad pointed out, there have been comments about similar effects in the past. I think it’s mental. I feel weird things with Zwift ERG mode as well, but lots of psychological stuff when you’re looking at a road going up and down.

Resistance mode in both (no paired controllable trainer, and set resistance to 15% in a separate app) and see how it goes.

I’m not sure if SIM mode uses rider weight or not. It does on my Neo 2T, and it gets a bit different if rider weight is different in different apps.

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Lol at #5. That ain’t it.

But I think the calibration could be playing a role. Sometimes I do it right when I get on, sometimes after I’ve warmed up, sometimes not at all.

Maybe to a lesser extent relative fatigue played a roll

The 66 min effort was recent and I’ve had consistent training since then. More recently I’ve done a couple of 30ish min efforts at 240-250 watts.

I think Chad may have something with the cadence/power not being as smooth as it should making ERG mode do lots of adjustments . The last time I used TR my cadence hung out in the high nineties/low hundreds. Now, after this long Z cycle, my preferred cadence seems to drop to the mid eighties

Again, I don’t actually care as long as I’m getting in that work and prepared well for my race. Thanks for all the insight though. Y’all are smart