How much power does it such from iPhone when it's connected via cable?

By zhouya

Source: https://global.rokid.com/blogs/max-2/how-much-power-does-it-such-from-iphone-when-its-connected-via-cable

2 watts to 5 watts on average. Basically same as you use phones.If you are worried about battery life, you can buy Rokid Hub, which supports charging while using, and say goodbye to battery anxiety.