Defaults are examples: R42/kg is a R380 9 kg refill (Alva, Gauteng, November 2026), and electricity tariffs vary by municipality. Enter your own prices for an accurate answer.
How we calculate it
Heater size: we multiply the room's volume by a heat allowance of 35–60 watts per cubic metre, depending on insulation. That's a common rule of thumb for South African homes, but sunny north-facing rooms need less and draughty rooms with high ceilings need more.
Gas cost: LPG holds roughly 13.8 kWh of energy per kilogram. An indoor, flueless gas heater releases almost all of that into the room, so an output of 1 kW burns about 72 g of gas an hour.
Electric cost: electric and oil-filled heaters turn practically all the electricity they use into heat, so 1 kW of heat costs 1 kWh of electricity per hour at full power. Thermostats cycle heaters on and off, so real-world costs are usually lower once the room is warm.
Compare the options in oil heater vs gas heater, or read our gas heater buying guide.