What are my options?
Cyclists are modeled by defining their power generation abilities over sustained time intervals. Given this is important, and not surprisingly there are ways to do this and they are not cheap.
One way is to use a formal lab. Another way is to spend hundreds of dollars and buy a power meter to attach to your bike. This has the advantage of providing feedback under actual riding conditions.
What if I don’t have an unlimited cycling budget?
But what if you don’t have money to burn. How might you estimate your power levels? Here is an inexpensive approach that you might want to be using even if you have a power meter and use labs. It begins with finding some challenging local hills and gathering their elevation gains, and the cycling distance to the top. As to elevation gains, you might use a Topographic Map, or a mobile phone app that can be used to get elevation. As to cycling distance, you can get that from any standard cycling device.
How do I measure my performance?
From that information, you can estimate the total work required to make the climb using the two simple equations provided in the Computing Climbing Effort section. Next you perform the ride and record your time. Then you convert it into seconds and divide the required effort in Joules to get your power expenditure.
How would that have worked for Pantini?
We have computed the effort to climb the Alpe d’Huze at 695,507 Joules. Marco Pantini made the ascent in 37 mins 35 seconds or 2255 seconds. Dividing the two yields a power output of 308.43 Watts per second.
Money vs. 10%
How well does this work? For me it is good enough that I am not running out to buy a power meter. You can make your own call.