IPSec tends to use AES, which can be 2x to 4x more performant than ChaCha20 thanks to hardware acceleration. And the power savings may be even greater than the throughput differences.
Should be added that this is highly dependent on the specific hardware. AES is cripplingly slow where accelerators are misconfigured or otherwise unavailable.
If you have a brain larger than your leg, you should consider configuring an IPSec endpoint to save power on your phone.
