Wattage shown on screen is very erratic

I have had a problem for about a month now. The wattage shown at the top of the screen is very erratic. For instance, if I am riding at 250w, the wattage will jump around constantly from about 220w to about 280w and everything in between.

This happens in all modes (free ride, erg mode etc). Just yesterday I did an 20 minute FTP test. I knew I wanted to maintain an average of 250w but because of the erraticism I couldn’t tell what wattage I was putting out.

I have the Power Display setting at 3 sec avg which always used to smooth out the wattage and worked well for me but now it does not.

Could you help, please?

My set up is Wattbike Atom running firmware version 1.02.01 with MacOS version 11.6.8 (MacOS Big Sur).

Extra info: this issue started happening at the same time as the problems with resistance not changing going up hills or in erg mode, so maybe something to do with the same release?

This is normal. This is a pretty small level of variation - remember you are not constantly pushing down on the pedals, there will be less output on your upstroke, and this will depend on your pedalling efficiency.

Some trainers use power smoothing to make the jumps less erratic.

It is not normal. At least it wasn’t until the release that also caused the lack of resistance going uphill. This has only been happening since then. I do expect some level of variation, of course, but it used to be much lower.

Perhaps my pedals stroke is reasonably efficient but if I was riding at 250w, I would expect variation between say 240w and 260w but generally pretty stable, especially with Power Display set at 3 sec avg. It is now far more erratic than it used to be.

Did you test it in some other app to see if it’s working correctly…this would tell you if it’s really zwift problem.

Zwift is the only app I use. I could test it by using the Wattbike Hub but, as I say, this was never a problem before about a month ago.

And for clarity, I’m talking about when riding consistently, like in a time trial, FTP test or in an ERG controlled workout. When I’m free riding going up and down hills or in a race I do expect more variation naturally.

I promise you it is normal. The Wattbike uses power smoothing (which is why you think it’s normal). It is likely that this has stopped working for whatever reason.

I would check your power output in the Wattbike Hub app first and see if it mirrors what you are seeing on Zwift. I would expect it to be identical.


I agree with James. It sounds like power smoothing for reporting has stopped working and you’re now seeing your real power figures. There’s no way you could hold actual power of between 240 amd 260w, I’m afraid, since there are so many variations in a typical pedalling stroke. Yes, power smoothing could fool you into thinking that you were never previously producing outside that range.


Wattbike recently made some changes to their power smoothing. There’s a checkbox located at:

Settings (Gearwheel at top right) > Profile > Ride Settings

It makes your power output look really smooth. My vanity outweighed my preference for truth for about 4 days, and then I changed it back.

As always, the key is not to look at the power number, because you’ll seesaw. Work out the cadence you need to maintain desired power in the gear you’re in, and then try to maintain that cadence.

If I do that, I can actually be quite a bit smoother doing workouts in resistance mode than I am in Erg mode. Humans 1 Machines 0 :joy:


Alternately, use a bike computer with a 30 second smoothing display. I often use that in TTs and just ignore the on-screen output (assuming you can connect a Wattbike to a computer via ANT). Both Garmin Edge and Wahoo Elmnt can show multiple power fields.

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Don’t tempt me to spend MORE money! :grin:

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Thank you everyone. This gives me a lot of good information. Yes Wattbike did update the firmware about a month ago. Maybe a combination of Wattbike’s smoothing and having the 3 Sec Avg turned on in Zwift has flattered me all this time.

I will try the new Wattbike power smoothing option and see how I go. Or maybe I just have to get used to the truth :confused:

Thanks everyone :slight_smile: