What's the cheapest way to heat a room? (Australia, priced per hour)

It’s July, the first no-rebate winter bills are landing, and heating is the single biggest reason they’re big. So here’s the question that matters most this month, answered with actual numbers: what does an hour of warmth cost, appliance by appliance?

The per-hour scoreboard

Priced at the guide’s working rates — 36c/kWh electricity and 4.5c/MJ gas. (Market averages currently run about 30–35c/kWh and 4–6c/MJ depending on your state, so scale to your own rates — it shifts the cents, not the order.)

Heater	What an hour costs	Why
Reverse-cycle air conditioner (split), delivering 2 kW of warmth	~17c	Moves heat from outside air instead of making it — about 4.2 units of warmth per unit of electricity
Gas wall heater (typical 15 MJ/hr living-room unit)	~68c	Burns 15 MJ every hour — and a share of that heat leaves via the flue before it warms you
Bar, fan or oil-column heater (2 kW)	~72c	Converts electricity 1-for-1 — every watt in, one watt of warmth out

Read that top line again, because it’s the finding most people refuse to believe: if you own a reverse-cycle air conditioner, you already own the cheapest heater in your house. The “aircon is expensive” instinct comes from summer cooling bills and old machines — a modern split delivers the same warmth as a bar heater for less than a quarter of the electricity.

The oil-column heater deserves a special mention because it feels economical — it’s slow, silent and doesn’t glow. It costs exactly the same to run as a bar heater. Slow heat is not cheap heat; it’s just slow.

Four things that change the numbers

• Your climate. The 4.2-to-1 figure is a temperate-zone seasonal average. It’s better in warm climates and lower in genuinely cold ones (alpine areas) — but even well below average, the split stays comfortably ahead.
• The thermostat, wherever it lives. Heating to 18–20°C is the sweet spot — each degree above that adds roughly 10% to the running cost, on every heater type.
• Filters. A clogged split filter can add up to 25% to its energy use. Two minutes with the vacuum, four times a winter.
• Room size. Close the doors. Half the volume heats in half the time, on any heater.

”Should I go buy a split, then?”

Here’s the honest version, because the numbers differ by where you’re starting from:

• Heating a main room with bar/oil-column heaters most nights? Yes — the upgrade case is strong. A split costs about $1,800–2,800 installed and typically pays for itself in 3–6 years on the heating saving alone. And the same unit is your summer cooling — running it in summer costs money like any air conditioner, but you never have to buy a second appliance for the job.
• On a gas wall heater? The running-cost gap is real but smaller, so the honest answer is switch at end of life, not before — on energy alone the payback for replacing a working gas heater is long. The maths changes if it’s your last gas appliance: dropping the gas connection saves the ~$300–400/yr supply charge before you count a single unit of heat.
• Already own a split and still running the bar heater in the same room? Just switch appliances tonight. That’s the single cheapest heating decision in Australia — it costs nothing.

The other half: stop paying to heat the street

Everything above is about the cost of making warmth. The other half of the bill is how fast your house loses it — and two fixes beat every heater upgrade on value:

• Draught sealing is the closest thing to a free heating upgrade: sealing gaps around doors, windows and floorboards can cut heating and cooling loads by 10–20% for minimal outlay — door seals, window strips, and closing the fireplace damper (an open flue is like a window left open). It makes every heater in this article cheaper to run from tonight.
• Insulation is the multiplier: an uninsulated ceiling leaks 20–30% of your heating effort skyward. Fix it once and the per-hour numbers above all shrink — on every heater, every winter, for decades.

Insulation gets the full priced treatment in the guide’s heating chapter — savings, cost and payback; draught sealing is covered there as the quick win it is. And draught-proofing is getting its own article soon.

The bigger picture

Heating is the biggest winter lever, but it’s one lever — here’s why this winter’s bills jumped and what a normal bill looks like for your household size. If you want every lever priced the way this article prices heaters — savings, cost, payback, including the upgrades that aren’t worth it — that’s the guide. And to see whether heating is even your problem, check your bill against homes like yours first.

Figures: 36c/kWh electricity and 4.5c/MJ gas are the sourced working rates from the Decode Energy Home Energy Saving Guide (AU 2026 edition); market averages re-checked July 2026 sit at roughly 30–35c/kWh and 4–6c/MJ by state, so our table runs a touch generous on the electric heaters. COP 4.2 seasonal average and the heater comparisons are the guide’s sourced assumptions. Your rates and climate zone shift the exact cents; they don’t change the order of the table.