Strava: Watts generated

[Rust Never Sleeps]

Good morning

Trying to understand the logic behind the Watt figures that form part of the stats on any ride. 2 riders ride together on a 60km route. Once done both have identical average speeds, distance, climbing meters etc.

Why does one have a power output say of 150 watts and the other 90 watts? 

[Duane_Bosch]

Good morning

Trying to understand the logic behind the Watt figures that form part of the stats on any ride. 2 riders ride together on a 60km route. Once done both have identical average speeds, distance, climbing meters etc.

Why does one have a power output say of 150 watts and the other 90 watts? 

The one weighs more than the other.

[Grease_Monkey]

The one weighs more than the other.

Yup, quite simple, more kg = more watts needed to move it all other things remaining constant. Quite a massive difference the steeper the gradient gets.

[SwissVan]

Strava calculated watts are a bit suspect

Or I’m an incredibly efficient cyclist (not)

[Grease_Monkey]

Strava calculated watts are a bit suspect

Or I’m an incredibly efficient cyclist (not)

Yeah, it is a little on the high side when I compare it to my indoor sessions with a power meter. My completely unscientific guess puts it at about 10% higher than what I think it really is.

[slickjay007]

As time passes Strava will tweak or change their algorithm for computing estimated power.

 

Also, regarding different readings, the estimated power can vary significantly between the device you use.

 

There is commonly a 10-25 watt difference between a Garmin Edge 1000 and iPhone. (The most common difference currently is about 10 watts on a ride.)

 

Also, some Strava estimated power as recorded by some devices is way off on wattage estimates for descents.

 

More important than the true or accurate measurement of what one's real wattage is as measured by a properly calibrated PM is that the Strava data is consistent. (Same effort in same circumstances using same device should be consistently the same.)

[RocknRolla]

I personally don't pay too much attention to that "power" reading it's basically the same as using a PowerCal HR Powermeter.

 

There are too many variables. 

[Wil6]

Wattage on Strava is far to inaccurate to go by. Just ignore it, or use a power meter

[Karman de Lange]

depends on bike you've setup (road/mtb) and weight you entered on your profile ... 

[Tristand]

It depends on the length/altitude-gain of the climbs/hills. The error factor is very high on small climbs especially since inertia plays a big role. On big climbs like mountain passes, power can estimated quite effectively.

[Andreas_187]

It's pretty meaningless since it doesn't know that you just cycled into a 50km headwind or tailwind

[RobertWhitehead]

The wattage is just a place holder of great things to come  . 

[riteshm]

The Strava power estimate is rubbish.  A friend of mine rode the Cycle Challenge 100 yesterday at 38kph average speed. Strava had his average power at 453 watts. He weighs about 70 kilos and is a decent B batch rider. At best his wattage should 240 NP, with the average I guess around 195-205 watts.

[Dgas]

The Strava power estimate is rubbish.  A friend of mine rode the Cycle Challenge 100 yesterday at 38kph average speed. Strava had his average power at 453 watts. He weighs about 70 kilos and is a decent B batch rider. At best his wattage should 240 NP, with the average I guess around 195-205 watts.

I rode the same race yesterday, my NP according to my power meter (Quark Dzero) was 253, Strava shows 235. Average speed was 38 in A group and I weigh 90kg. The Strava numbers never agree with the PM reading. Trust my PM and not Strava.

[Karman de Lange]

The Strava power estimate is rubbish. A friend of mine rode the Cycle Challenge 100 yesterday at 38kph average speed. Strava had his average power at 453 watts. He weighs about 70 kilos and is a decent B batch rider. At best his wattage should 240 NP, with the average I guess around 195-205 watts.

Strava assume you riding alone with no wind, bunch riding will throw power of completely.

 

I find it actually very close to what my power meter reads (within 10%) on normal day riding alone.

[bertusras]

I think everyone is confusing the actual question with the unreliability of Strava's power estimation.

 

The poster asked why the estimated power is different between two riders who rode the same route together. Only Duane and Greasy_Monkey actually answered the question before it digressed, until Karman pointed out another important aspect which forms part of the algorithm.

 

To answer the actual question. Are both rider weights, bike weights and bike types correctly entered for both Strava profiles? If they are, the only reason why the one is higher than the other, is that the higher one has more weight to lug around.