A typical phone battery has a capacity of about 13.5 Wh. Assuming a converter efficiency of 90%, it takes 15 Wh (0.0015 kWh) to charge your phone from an outlet. Assuming an electricity cost of $0.39 per kWh in San Francisco, that's 0.58 cents ($0.0058) every time you charge your phone using the solar panel.
haha it's not the savings. It's the accessibility! This phone is out on a balcony by a herb garden. The big annoyance with electric devices is that they need to be connected to an outlet. PVs have saved this.
We have our blinds on PVs which is very convenient. No charging required and no wires required. Same thing applies here. The PVs allow battery recharge for places where power cables are inconvenient. The phone is a convenient tailscale device with a battery that can webcam!
By Grabthar's Hammer, what a savings.