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What is Virtual Power, and How Does it Compare to a Power Meter?

What is Virtual Power, and How Does it Compare to a Power Meter?

One of the interesting features in the software and hardware of the RF-1 is something we like to call Virtual Power.  Why do we call it Virtual Power?  

Most power meters measure force directly applied to the bike, such as a crank arm or wheel hub.  These are the direct force measurement power meters we all know and love (unless you're Alberto Contator).  This is also the most accurate way to make a power meter.

Another way to measure power is to calculate the forces working against the bike, and using the bike speed, calculate the power which is required to match these forces.   There are four main forces on a bike: wind, rolling resistance, gravity, and acceleration.

While it's tricky to measure air resistance directly, we use some equations which take into account your body size and shape to help make a more accurate estimate.  We can also measure weather conditions directly (like humidity, pressure, and temperature) which means we can get a more accurate picture of the air resistance.

Rolling resistance is also tricky to measure directly, but we have a good resource of estimates based on tire type and conditions.

Fortunately, both acceleration and gravity are easy to measure directly.  It's preferable to measure the slope directly instead of basing it on elevation changes over distance, and with our sensors, we can do exactly that.

Science aside, what does this all mean?  It means we can get a more accurate power estimate than you might be used to if you've seen them before (for example, Strava).  However, we are still going to fall short of a direct force measurement power meter.  Different cases will yield different results: a long ride up a hill without much wind will be pretty accurate, a group ride where you're hiding from the wind ten wheels back at 25mph will be less accurate.

We think Virtual Power a great tool for people who don't already own power meters, who might like to see a number that while not perfectly accurate, could be very informative in their riding and training.