The cost of charging the BMW i3 mainly depends on the electricity price used and the charging method. According to data provided by BMW, the range of the BMW i3 can reach 260 kilometers on a full charge. Assuming that 12 KWH of electricity is consumed per kilometer, then the cost of each full charge is the amount of electricity consumed while charging multiplied by the price of electricity. For example, if the electricity price is 1 yuan\/KWH, the charging cost is about 12 yuan. However, it is important to note that electricity prices and charging methods may vary from region to region, so the actual cost of charging will vary.