So 20 units per 1 full charge?
1 unit costs LKR 45 (http://www.ceb.lk/for-your-residence-2/).
20 units = 900 LKR = 1 Full charge.
You can buy 7.692 L petrol for 900 LKR. If your fuel economy is 12 kmpl, that can take you 84 kms. AFAIK, a leaf can take you 160km per charge, making the Leaf...