Strava shows inaccurate power data

I've noticed issues related to power measuring/output/estimations. 

It appears that for some reason when using a power meter (Garmin Vector/Edge1000) Strava appears to "downgrade" the ride by approximately 15% (both average power and NP), yet when using the Strava iOS app the power ESTIMATE as compared to an actual power meter is about 15-20% MORE than what the power meter is demonstrating. I can see 1-3% differences, but these are huge. I've taken to not relying on Strava for much of anything except for cataloging my rides. 

How in the world can anyone even trust the Strava data? The only thing that appears to be accurate is timing and distance. Even then I've seen minor discrepancies. 

Why is this occurring? Anyone with similar issues? I've got a "ticket" in the queue, but two weeks out and I've yet to hear anything back. 

I've taken to using Garmin Connect since the data is consistent with what the Edge 1000 is reporting. At least I can gauge my performance with some consistency. 

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  • Same here. After a ride yesterday where my Garmin recorded an average of 270 watts Strava presented me with 236.
    Frustrated by this, I searched and came across this thread, as Matthew R points out, going back over two years. It seems Strava manipulates our data to make it consistent with people using the least accurate devices - probably a basic phone running the app. This is not acceptable for users wanting to accurately monitor their training, and in most cases paying Strava the premium fee for them to skew our data from what has actually been recorded. .

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  • Such a long thread and apparently no resolution.  I just did an erg workout on my Elite trainer and Strava shows a consistently lower power measurement than was showing on Zwift.  Guess I'll see how it compares with some other systems.

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  • Strava is still doin this I notice for a few months. Even today I did short 'reactive' sprints, just one or two secs to 'jump on wheels' but none of these 800w values show, strava shows max 400w. The overall power/normalised power are close but totally removes all my peaks

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  • Subscribed to Summit (new Premium).

    Today did my first ride with power meter.

    Noticed wrong numbers

    Found this thread

    Summit canceled.

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  • Hi!
    I have noticed that Summit indeed displays NP as per the Coggan formula. It is displayed on the resume of the ride, but only on the PC. On iPhone app, there is no change (assume yet) - still the strange Strava-Ava rage-thing nobody really knows what is. The new statistics in Summit is to me a clear improvement.

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  • Same here. Strava shows to low power readings compared to what was actually recorded on my Garmin edge 810. Real bummer...

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  • More bad data on Strava. The power numbers from zwift reported on strava appear to be completely fabricated.

    Just noticed a recent workout in zwift, and the power numbers are all over the place. Some laps show higher, some lower -- by huge amounts 120W differences in some laps. This was an erg mode workout, so power should be right on. And Golden cheetah reports the correct wattages from the same workout, so it's not the fit file. I just submitted a support request. This is ridiculous.

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  • I'm not even using a power meter, however my mate (also no power meter) and I did a ride today. He is about 25kg lighter than I. He was a little slow today so I had to wait a few times for him. Overall I completed the ride about 4min faster moving time. Somehow my av. power was 158 while his was 164.... This happens all the time. Go figure.

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  • Mark please don't even bring up "virtual power" in this thread. It's completely irrelevant from every aspect.

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  • Mattias, thread title: Strava shows inaccurate power data.

    My post is about Strava showing inaccurate power data. Last time I checked, those two things sound pretty related.

    You having a bad day mate?

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  • I've been using a Polar v650 recently and for some reason the power data from that (as seen on the Polar Flow web site) match with Strava. Switched over to my fenix 3hr last week and Garmin Connect shows 127 watts average for 2 hour ride (Stages gen 1)......Strava 92 Watts. Looked back at my other years of using a garmin with power and notice the differences. I've been a premium member since 2012, but now headed back to basic membership. 

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  • To the guy with the Quark DZero,

    The reason that Strava showed half the power with the power meter connected to the app via Bluetooth is because Bluetooth was only broadcasting one channel I.e. left side power. Connected to a head unit, Garmin Wahoo etc they recognise this and double the reading. The ANT+ broadcasts both channels so you get L+R = Watts not Lx2 = Watts. The only way to fix the issue would be to have the ability to tell the power meter to double the left side Bluetooth broadcast (Favero Assioma has this option) or have a firmware update to permanently broadcast both channels via Bluetooth, or the most unlikely would be to have an option in Strava to double the power meter reading.

    Best option is don’t use Strava to record anything. Just upload from Garmin Connect, Wahoo, Training Peaks etc.

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  • Realize this is old thread and Strava will not fix, but I have interesting results with my various PM’s. SRM, Pioneer both generally get significantly downgraded on Strava(5-10%), Stages come in closer but still slightly under, but Vectors show up about 5-10% higher.....so comparing rides/workouts on different bikes is impossible.

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  • Recently bought a power meter and was excited to see the extra data in Strava.  Now strava is overwriting my actual power data with their fake "estimated power" that they were applying before I had a power meter, and it's consistently 20% lower than my real power.  Getting a power meter has not just added no actual data to my strava experience, it's giving me inaccurate data.  Think this will be the end of my summit subscription, since I'll now need to use outside apps to accurately analyse my rides

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  • Alas, the silence from Strava is deafening. I was hoping to use the power tools like power curve, TP estimate, and fitness and  freshness charts as an all in one replacement for WKO etc. But with the inaccurate capture of data I have cancelled my Summit membership after 7 years.

    I am recommending to all my followers on Strava and Insta they do the same. That is about 2000 people #strava if you care.

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  • What makes it more frustrating is that I, like many, upload accurately gathered data having invested in the best sensors I can justify/afford, including using IFTTT and a smart scale to ensure that my weight is always up to date. My age is also correctly entered. Yet contacts I follow who never bother with all this, and upload their rides from a smartphone with no HRM, cadence or power and leave their weight at the default ‘less than 124lbs’ get vastly inflated estimated power figures, which they honestly believe to be accurate, because Strava couldn’t possibly be wrong.

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  • bummer, a lot of the cyclists here  care about data accuracy and integrity. I use GC and TP for data analysis but it would be nice if you can trust the power numbers on Strava. 

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  • anyone found a workaround for this problem?  I can't believe they haven't fixed it.

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  • Pretty shocking this problem still exists. Just noticed that my outdoor rides with Garmin show approx 10% more power average than Strava despite me having disabled zero power

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  • Sad that this is still an issue on Strava.  Speaking as a Senior Software Engineer, the data is the data.  I've never personally worked on or implemented a system that changes data from the authoritative source.  In this case it's the sensors that generate the data and the cycling computers that collect the data from the sensors.  This is the major reason why I have not signed up for Strava's premium service.  Why would I pay someone to change the data I worked hard to achieve.  Basically, Strava is asserting that the power meter, sensors, and cycling computer that I've paid good money for are all wrong.  

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  • Just discovered this issue for myself while looking at the values Wahoo provide within their app and compared to Strava my average power is down by about 7%.

    Could it be that Strava include all the time the PM is reading zero? Wahoo has an option to include or exclude zeros in your averages.

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  • Well, I have a big issue also with the max power data. 1203w on Wahoo and Training Peaks. 1159w on Strava. What has Strava done with those 44w? That's quite a big difference and utterly pointless. The data is the data as Kelvin said. Strava has no right or reason to change it. 

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  • Strava needs to stop overwriting sensor data with is own sh#te calculations.

    Speed sensor is overwritten along with distance...

    Power meter is overwritten with nonsense.

    it doesn’t really matter as it’s just for logging rides, but still irritating especially if you put in a decent effort and would like others to see.

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  • If Strava has an issue with mapping in true power data into its common power fields. A pragmatic and most likely simple solution would be to add additional power fields if such data available in the upload file. E.g telling that the "true" powerdata comes from a Garmin device, that the avg power is xxx and that thet the Normalized power is yyy. If any other of the garmin power fields also would be present I would not cry.

    The down side is of cause that it will look bad when the numbers are off with 15-20% :-) A solution to that is to make the presentation of power data configurable in the user profile.  

    If this was available I would become a paying user.

    p.s with power meters becoming more coming more common I assume we will see the difference between Strava estimates and "true" numbers decrease? After all its a great opportunity for an AI programming task with all data the is available.

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  • It took me forever to figure this out, but most of us have our head units set to not average in zeros for average power. Garmin connect shows us the power like we have it set up in the head unit. For example, if I do a trainer ride the power in Garmin and Strava is the same. If I ride outside and end up not peddling, I get a difference. For a flat ride where my average power and NP are very close, Strava power is also very close.

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  • I see what you’re saying George Birdwell, Strava replied to me with the following:

    “Thanks for your message, sorry for the confusion. We may be processing data differently than your Wahoo device. Wahoo tends to use summary data to calculate these figures, whereas we use all data that is recorded in the file. There will be differences between the Weighted Average Power and Normalize Power. How much and which direction will depend on the ride. Typically, for shorter rides, Weighted Average Power will be lower than Normalized Power. This is a result of the different types of smoothing used by the algorithms. Both numbers have been used successfully by professional coaches.”

    Trouble is they don’t seem to use ALL the data recorded in the file, peak power will often be reduced by Strava - I had this happen last week on a Wattbike ride where they dropped off 33w from my peak power, due to their “algorithm”

    Personally I would prefer if Strava report back what the power meter reports, and save the made up figures for their estimated power for users without power meters.

    It’s also interesting that despite having power data to work with when I upload a ride on my 2nd bike with no PM Strava estimated power almost always shows a lack of meaningful work in Zones 2-5 which is completely the opposite of the data shown in rides with a PM, instead they show huge volume in zone 1 and 7, this is despite having actual power files to work with from the same user.

    I think that considering we pay a premium for this service it’s not great to see data manipulated so much, when all we are asking for is the accurate truth of how we performed!

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  • Still an ongoing issue.    

    Strava power numbers still much lower than that recorded on various devices with various power meters.   

     

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  • And actually most of us set our recording devices to average in zeros for power data.        We do not average zeros for cadence data however.     

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  • Geez guys, stop complaining, you've got all your social media content in Strava now to be thankful for, who cares if your data isn't accurate?

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  • Still an issue, with Wahoo units also.

    Wahoo ELEMNT data and Training Peaks both show A recent ride at 277W, Strava is showing 251W. This is just one example of many.

    Rather than explaining Strava’s way of processing data, please explain why you wouldn’t just import the RAW data like TP does? What is the benefit of your method?

    Thanks in advance

    Alex

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