Taking the mobile phone battery as 5000mAh and the charging voltage as 5V, for example, it takes 25Wh to fill it once, plus the influence of factors such as charging efficiency, if calculated according to the consumption of 30Wh of electricity, three times a day, it is less than 100Wh, that is, one tenth of a degree of electricity.
Maybe this algorithm is not accurate enough, but in reality it will not exceed too much, so it can be basically ignored. Otherwise, all mobile phone users will worry about the cost of charging.
From the use of mobile phones to now, I have not heard that people will struggle with charging costs.