Why does City Power deduct R241.50 from your first vend of the month?
On the standard Prepaid High tariff, City Power charges a fixed monthly amount just for keeping your meter connected: R70.00 for a service charge and R140.00 for a capacity charge, both ex VAT. Adding 15% VAT brings the total to R241.50 per month.
Because you do not get a monthly bill on prepaid, this fixed charge is recovered directly from your next vend. So when you buy R500 of electricity on the first of the month, the meter sees R241.50 already owing on your account and diverts part of your vend to cover it before you get any units.
The Prepaid Low tariff (registered indigent households) has no fixed monthly charge, so no arrears recovery kicks in and every ex-VAT rand buys units.