This is why I use the eFTP from Intervals.
I think it is probably similar to zFTP being they both come from a critical power curve.
This is great for training.
Unfortunately, training is not a clear goal in Zwift.
They kind of backed into the critical power curve in an attempt to fix racing.
I’ve not looked at my zFTP because I’m not sure where it is posted.
I like the layout of info on intervals.
Look at your profile on the zwift.com website (go to My Feed, and then click on My Profile, then click on More Info for the most detail)
I know I said that I wouldn’t peek at my CE stats, but peer pressure became too much 
My zFTP value is only 2W higher than my FTP derived from Zwift’s “FTP (shorter)” workout. What consistency! Unfortunately, both are pathetically low 
Ok, I just looked.
My zFTP is 212 and eFTP is 208.
I set my work out FTP to 218 (add about 5%) because it gives me a goal.
I don’t like logging into what feels like a 3rd party site called Zwift.com.
The other 3rd party site gives more info and I can use outside.
Still, the CP curve for CE appears good.
The zFTP calculation does not require as long of a max effort to be calculated as #2. This is one reason it’s better to use this for race categorization rather than 95% of your best 20 mins on Zwift.
Now, for people using Zwift that have never done a max 20min effort or FTP test, which do you think is a better estimation of their FTP: zFTP, or #2?
I’ll vote.
I think zFTP would be better, even if they have not done a hard effort.
If they enter a race, they maybe in an incorrect cat but the data from that race will update the curve.
You didn’t state weather we wanted it for racing cat or workouts.
If you do easy workouts and never push, then there will be no data to correct.
Again, this is an area where Zwift have 3 criteria.
Use zFTP and get rid of the other 2 options.
Just like race cats- 2. ZP and CE.
Get rid of one.
Make everything based on the CP curve and move on a fix other stuff.
That is not what we discussed you said there are 3 FTP’s I said that the first two you listed are just ones value stored in Zwift. We never discussed zFTP?
I don’t think I can answer this without 100% understanding zFTP but if zFTP can use a short duration to get accurate FTP data then it is the best to use. I do think zFTP is a good value to use for racing. I also think if you do a full range of tests over the whole spectrum of power you will get a good value from zFTP to use for training, but you would probably get the same value from a 4DP test or a classic FTP test.
But once you start reading on FTP estimation you will find there is multiple ways to get to a FTP value.
Just so I’m clear, when people say that zFTP is Zwift’s way of representing or telling you your FTP – by definition it’s saying that it represents your maximum sustainable effort for 1 hour? And if one does a 1hr FTP test and has a different result, then which is actually a more accurate representation of FTP?
No one said one hour.
That’s the defined time of what FTP is based on. Not half hour, not 2 hrs, etc… I’m just wondering if Zwift is unique or not, in calling something xFTP based on cherry-picked best values from multiple efforts’ results at different points on the time curve.
Read the link David posted. Anaerobic threshold (FTP): why you might be overthinking it — INSCYD
Ok, so is Zwift using a not-so-well-known and/or obscure means of calculating AT/FTP that will require even more explanation to the masses? ie. why doesn’t the Zwift platform’s own FTP test determine my zFTP?
If I understand you correctly… almost nobody does hour record attempts, so it would be pretty hard to base a categorization system on something people don’t do. Even a “proper” 20 minute FTP test result is just a prediction of what might happen over an hour, but what actually happens is typically unknown. I’m in the camp that says zFTP should be called something else, but its lack of a 1 hour duration is not really the confusing part, since other measures are also based on a prediction derived from a shorter effort. Ideally we would see people fully populate the CE power curve with max efforts, so it would be great to see an effort around achieving that outcome (thought exercise!). If we did there would probably be fewer situations like mine where it deviates significantly from 20 minute tests.
Perhaps there should be a training plan designed to populate the CE power curve. Of course those who want to game the system would not do it, but probably some people would in the interest of getting a valid result from the calculation. Some would end up in a lower category by doing it.
Did you read Dave’s posts above. The answer was is there.
I’m out 
So, has it been said why zFTP isn’t becoming the default for FTP and automatically put into your profile for workouts, etc?
I don’t think so, but since CE will calculate something based on very little data (eg, 5 minute ride) there will be many situations where it’s way off from the result of an FTP test of any kind, even a ramp test. A person with little data in the game will have some kind of zFTP value (whatever that means in this context) but it won’t be anything remotely like their FTP.
Fair enough, that’s been said above, but this should then be explained in the FAQ – specifically that if you haven’t been doing any maximal efforts (ie. just doing some casual group rides, meetups or training sessions (based on guessed ftp), then it will not be accurate. I think this goes back to suggestion that users should have option to increase their zFTP if they see fault with it (but not decrease).
I guess the straight question to ask, is zFTP supposed to be the means of estimating what standard FTPs would be (as determined by a standard FTP 1hr test), but without having to rely on the universe of riders actually putting themselves through that exercise?
Yeah I think these values serve two different purposes. zFTP is intended to come up with some kind of result that puts a person in a race category as quickly as possible (looking at it from a product perspective). There are reasons to game that value but you just hope that eventually it sorts itself out.
FTP is intended to help a person who wants to do valid workouts, so there’s no reason to game that. If it’s too high you can’t do the workout at all, and if it’s too low the intent of the workout won’t be met.
It would be better to say that the zFTP value (or whatever you want to call it) is a race categorization based on available data of any kind, which may be wrong, whereas if you want to do a workout and your FTP is unknown, then it’s simply unknown and you have to do a test of some kind to find out.
I think we and Zwift should just use the zFTP value.
That is a good value to enter for workout FTP.
In work outs, we have the ability to adjust the workout bias +/- 25 %.
I adjust my FTP up by 5% but could also use the bias in the work out.
I don’t really see a reason why we have to have the ability to manually adjust our FTP anymore.
Zwift should just fill in the zFTP and be done.
I also don’t think people should try to compare one metric to another metric if they are measured differently.
It’s apples to oranges.
95% 20min FTP is not going to be the same as a full 1 hour test and will be different from the zFTP or eFTP calculated from a critical power curve and the ramp test is different still.