Bicycle Power - How many Watts can you produce?

Clothes slow Lance down

Clothes slow Lance down

I love watching the Tour de France each summer and I enjoy watching the coverage and seeing the cyclist's wattage as they race away from the peloton or climb the Alps. By understanding how much power a person can produce, it should give you a good frame of reference on the scale of electric power production!

As I watch the Tour they occasionally display a rider's instantaneous power output on the screen.  They are able to do this because the cyclist has a power meter on their bike and this transmits data to the broadcasting network.  So just like the TED can monitor my home's power consumption, the bicycle power meter measures a cyclist's power production.  This power usually ranges anywhere between 250 Watts if they are just cruising along with the pack, or 400-500 Watts if they are pushing hard up a steep climb.  To see another example of a cyclist's power watch this Olympic cyclist power a toaster

A Watt is an instantaneous measure of power and is a product of force and speed.  In electrical terms, the force is Voltage and speed is current (Amps); therefore, electrical power is Voltage * Current. For a cyclist, the force is how hard he pushes on the pedals and the speed is how fast he turns the crank (rpm).  The combination of these two things results in the cyclist's power output, which is usually expressed in Watts.   Remember, you need force and speed to get power.  If you go to spin class you may see those cyclists spinning the crank very fast, but their power may not be that high if they dont have a lot of resistance - which requires more force by the cyclist - on the wheel.  For more on this topic, see the great FAQ section that has been put together on this page dedicated to bicycle power generation.

The International Cycling Union (UCI) maintains records for the Hour Record, which is an ongoing contest to see who can ride the farthest (measured in km) in one hour.  To get a good estimate of the maximum energy a person can produce (these are elite athletes after all), we'll figure out the average wattage of someone competing for the Hour Record, and since it lasts an hour, this average wattage will be the total energy the rider expended over that hour.  Therefore, the energy they expend over the time they compete can be presented in Watt-hours.

The current record holder for the Hour Record is ex-pro cyclist and 2012 Tour de France winner Bradley Wiggins.  In his book on his hour record chase, My Hour, Wiggins discusses how air pressure affects speed.  Air pressure is a force acting against the cyclist, so the cyclist has to put more force on the crank to overcome it.  If it is desired to maintain a constant speed, and air pressure increases, force will also have to increase to maintain the same speed (from Newton's third law: for every action there is an equal and opposite reaction). Wiggins states:

For every 20 millibars the air pressure goes up, your lap time increases by 0.1 sec.  For example, in Manchester I had been travelling at 55 km/h in training, which roughly equated to Tony Rominger's second record; on days when the pressure was 990 millibars I'd do 30 minutes at 55 km/h putting out 410 watts.  My aerobic threshold is between 420 and 460 watts, so putting out that power I could have kept going at that pace for an hour and a half.  That was why we started working towards the 55 km target.  In London on the day, however, because the air pressure was 1,036 millibars, to cover 54.5 km in the hour I had to average 440 watts; to stick to that 55 km/h schedule would have taken 460 watts, which I couldn't sustain.  The pace I went depended on the pressure on the day. 

Wiggins did end up doing about 440 Watts as his final distance was 54.526 km!  If Wiggins' bike were attached to a bicycle generator and it was super efficient, Wiggins would have been generating enough power to light up 7 60-Watt light bulbs!  Since I pay about 10 cents/kWh, if I were to pay Wiggins for the energy he produced over the hour he was pedaling he would have almost earned a whole nickel (440 Watts • 1 hour = 440 Watt-hours = .44 kWh)!

Hour-watts-power-outputThe cycling blogger Alex Simmons has a great article on the current Masters Men (35-39) Hour Record holder Jayson Austin and his power output over his attempt at the Master's record in 2009.  Jayson's average power output was 302 Watts over the hour he rode.  The year before Jayson tried to go for the record but was only able to produce an average of 241 Watts (he wasnt feeling too well, so you can see his power output decline the longer he rode).  The graph of the two attempts can be seen at the right.

As you can see, the best human efforts at producing power over the course of an hour on a bicycle are around 300-400 Watts.  To put this in perspective, when my AC is running full blast my house can consume about 4,000 Watts or 4 kW.  I would need over 10 of the best cyclists in the world attached to bicycle generators to power my house when it is consuming this much power!  While this doesn't diminish the effort of the cyclists, it does demonstrate that powering our future by pedal power doesn't look like an option, unless they want to work for nickels.....

November 2009 issue of Bicycling magazine has an excellent article on human powered bicycle generators that I highly recommend.  As someone who is passionate about renewable energy and cycling, I get very excited reading this stuff.  The article mentions two companies that are trying to retrofit gym equipment and spin classes to produce and display cyclists power output.  ReRev is retrofitting gym equipment to produce clean energy and The Green Revolution is doing something very similar and targeting spin classes.  I've wanted something like this in my gym for awhile.  I'm not a big fan of spin class currently because there is no feedback on how I'm performing and improving.  These companies can provide valuable feedback on your power output AND produce clean, renewable energy for the grid.  This is win-win stuff.

BTW, we're working on a new site all about cycling power output and comparisons.  Check it out. crankwatts - bicycle power comparisons

Check out this related products on Amazon:



If you're interested in generating electricity from a bicycle check out our post on Human Bicycle Power Generation.

Going further on the topic of human bicycle power output, here's our post on how many cyclists it would take to replace a nuclear power plant!

Check out this cool video from SportsArt Fitness introducing the new ECOFIT Networking System for their electricity-producing Green System.

Associated Press - Oregon gym installs power generating equipment

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Unfortunately I dont think that would work. In my simple comparison, I assumed there was no inefficiency between the power output of the cyclist and creation of electrical power, so this is already the maximum power expected. I agree that it would be very cool to see a demonstration of a bunch of riders powering some devices!
Plus, you have to feed, water, and cool the human generator - further diminishing the efficiency.


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