There are a couple of power meters that will work on a SRAM Apex crankset:
Left Crank Arm Power Meter
Stages Cycling makes a left arm power meter that should fit the SRAM Apex crankset. It’s important however to know if your Apex crankset uses a 30 MM or GXP style spindle, as this will determine which Stages power meter will fit.
BB30: Stages Carbon for SRAM BB30 Power Meter with Spindle B
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: Easy to install, don’t have to change crankset
Cons: Measures left leg power only
Power Meter Pedals
Power meter pedals can be installed on any crankset. This is a very popular power meter type as they fit any bike, are easy to install and can be moved from bike to bike if necessary. We carry power meter pedals from Favero, Garmin, SRM/LOOK and Wahoo. This includes pedals for SPD-SL, LOOK Keo as well as Speedplay cleats.
Pros: Easy to install, works on any bike, can move from bike to bike, don’t have to change crankset