I've got the Alva mini gas heater:
These are the specs:
Let's do a calculation to determine which is cheaper, Eskom or gas.
The cost for a 3 kg gas refill is R86.
The heater consumes 165 g/h of gas to produce 2.5 kW of heat power.
The energy produced for one refill is 2.5 kW × 3000 g ÷ 165 g/h = 45.5 kWh.
The cost for gas is thus R86 ÷ 45.5 kWh = 1.89 R/kWh.
Your Eskom cost is 2.10 R/kWh.
So gas is the winner.