There are several power meters that will work a Cannondale One road crankset:
Left Crank Arm Power Meter
Stages Cannondale Hollowgram Si Power Meter
The Stages power meter is compatible with Cannondale One cranksets. The power meter replaces your left side crank arm and measures left leg power only.
Please note, these power meters attach a sensor to the inside of the left crank arm. On some bikes, there is not enough room between the left crank arm and the chainstay for the sensor to clear the frame. Therefore, you should make sure you have at least 10 mm of clearance for Stages power meters. Also, please make sure that you don’t have a bottom bracket mounted rear brake (used on some aero and TT bikes). Please refer to the image below.
Pros: Affordable, easy to install, don’t have to change crankset
Cons: Measures left leg power only
Spider Power Meter
power2max Cannondale Road Power Meter
The power2max power meter is also compatible with Cannondale One cranksets. This power meter will measure the power produced by both legs. power2max makes wonderful power meters, we use them on our own bikes.
Please note, some Cannondale cranksets come equipped 120 BCD chainrings or with direct mount chainrings (spiderings). In these cases, you will need to purchase a new 5-bolt chainring for use with your power meter. We recommend Praxis chainrings with this power meter.
Pros: Moderately priced, VERY reliable, don’t have to change crankset, measures both legs
Power Meter Pedals
Power meter pedals can be installed on any crankset. They are reliable, accurate, easy to install and can be moved between bikes. We carry every power meter pedal available including ones from Favero, Garmin, SRM/LOOK and Wahoo. This includes both single- and dual-sided versions as well as pedals for SPD-SL, LOOK Keo and Speedplay cleats.
Pros: Easy to install, works on any bike, can move from bike to bike, don’t have to change crankset