The June Bill Shock: Stop Heating Rooms You Don’t Use

Every year, late June and early July, the same conversation happens on social media: my bill just landed and it is hundreds higher than last quarter. The advice that follows is always the same. Switch off appliances at the wall. Take shorter showers. Check your standby load. None of those are wrong, but in a cool-climate household none of them are the answer either, because they are spread evenly across a house where the bill is not.

I ran every state through the heating cost calculator. Here is what is actually paying for your June bill.

The shape of a winter bill

Below is the percentage of the winter quarter bill that goes directly to space heating in a typical 2.7-person household, using the Australian Residential Baseline Study averages weighted for seasonal load. Two scenarios per state: gas central heating (still the most common in cool states) and reverse-cycle heat pump.

Based on per-state appliance kWh-equivalent figures from the Australian Residential Baseline Study 2021, seasonally weighted (75% of annual heating falls in the June to August quarter for cool zones, 60% for temperate).

In a Canberra household with gas central heating, almost four out of every five dollars on the winter bill is paying to warm air. In Brisbane it is one in three, and most of that drops to standby load and hot water territory if the household switches to a heat pump. The action list has to follow the cost.

Why your house is warming rooms you are not in

Central heating (gas ducted, ducted reverse cycle, or slab-electric) was designed around a 1960s assumption that the household was awake in different rooms at different times and heat-up time was the bottleneck. The thermostat sits in one location (usually the hallway), the ducts feed every room, and once it is on, it is on.

Modern households use central heating differently. Two or three adults spend most of their evenings in one room (living room, kitchen, or home office), sleep in one bedroom, and ignore the other three or four rooms entirely. The ducted system is heating all of them. The bedrooms get warm at 6pm even though nobody walks into them until 10:30pm, by which time they have cooled again. The spare room gets the same dose. The energy is real, the radiating heat into and back out of the walls is real, and it lands on the bill.

Lever one: behaviour and tariff (free, partial)

Five things you can do this week, no spend, all renter-friendly:

1. Drop the thermostat two degrees. Every degree below 21°C is roughly 10 percent off the heating bill. 19°C in a jumper is still warm. A Melbourne gas-heated household spending around $900 on winter heating saves about $180 this quarter alone.
2. Close the doors to rooms you do not occupy.Bedrooms, spare room, hallway side rooms. Ducted systems with dampers should be set to feed only occupied zones; ducted systems without dampers should have the registers in unused rooms physically closed. This alone is typically a 15 to 25 percent cut.
3. Heat on a timer, not on a thermostat. Most ducted systems can be programmed to only run during occupied hours (say 6pm to 10pm, then 6am to 8am). The cycling cost of an unattended heater filling rooms you are not in for the remaining 18 hours is real. Worth around 10 to 15 percent.
4. Switch to a time-of-use plan. If you are still on a flat-rate tariff, ask your retailer to switch you. Most heating happens in the evening peak (4pm to 9pm) on a time-of-use plan that is the wrong window. The fix is to pre-heat in the off-peak shoulder (1pm to 4pm) and ride the thermal mass through peak. Requires a smart meter, which the retailer will install for free in most states.
5. Sleep cold, not warm. The cheapest unit of warmth in winter is a thicker doona and an electric mattress pad (50–80W for a few hours vs 3,000–6,000W for a heater). Heating the bedrooms overnight is the most expensive thing a cool-state household does.

None of these requires spending a cent. Stacked together a disciplined cool-state household can take 30 to 50 percent off the winter heating line.

Lever two: small spend ($80 to $2,000)

Three retrofits in rough order of dollar-saved-per-dollar-spent:

1. Door snakes and weatherstrip on the doors between heated and unheated rooms. $30 to $100 from any hardware store, half an hour to fit. Cuts the leak from your living room into the cold hall by 50 to 80 percent. Worth around $80 to $150 over a single winter. Renters can fit this without landlord sign-off.
2. Heavy curtains with pelmets on the windows of the rooms you actually heat. $300 to $800 installed. Most winter heat loss in a typical brick-veneer Australian house goes through the windows. Pelmets are the critical detail because they stop the convection loop above the curtain. Worth around $150 to $300 a winter, payback inside three years. Renters: most landlords will sign off, but check first.
3. Top up the ceiling insulation if you have less than R3. $1,200 to $2,000 for a four-bedroom house through a Sustainability Victoria-style installer. Around 30 to 40 percent of heat loss in an Australian home goes through the ceiling, and most pre-2000 houses have R1.5 or less. Worth $300 to $600 a winter in cool states, payback inside five years. Owners only; the installer needs roof access.

Three cool-state deep-dives

Melbourne: gas-ducted is the line item

A typical Melbourne 4-bedroom household uses about 41 GJ of gas a year on space heating alone, at the current VIC blended rate of $0.038/MJ. That works out to around $1,560 a year just for the heating fuel, of which roughly $1,170 falls between 1 June and 31 August.

The standard Melbourne advice is to switch to reverse cycle. That is correct and we have written it up at length elsewhere. But the relevant point for this winter is: before you switch the appliance, switch how you use it. The same household, dropping the thermostat from 21°C to 19°C and zoning the heating to the two rooms they actually occupy, will see the gas heating bill for this winter quarter come in around $750 instead of $1,170. That is around $420 off the next bill without spending anything.

Hobart: more electric resistance than people think

Tasmania is the state with the highest baseline household electricity consumption in Australia (around 11,000 kWh a year for a 4-bed) precisely because so much of the heating is still resistance electric (panel heaters, in-slab, fan heaters). At the TAS retail rate of 27 cents and around 10,500 kWh a year of heating-only consumption, a typical Hobart household running resistance heating across all four rooms is spending around $2,130 over the winter quarter on heating alone. That is the single biggest line on the bill by a long way.

Resistance heating is by far the most expensive way to convert energy into warmth: one unit of electricity equals one unit of heat, where a reverse-cycle unit gets you three. The behaviour interventions above bite hardest here because every kWh you stop using is a kWh at full retail rate. Closing the doors and heating only the living area cuts that $2,130 figure to around $1,170, a saving of nearly $1,000 in a single winter before any retrofit is considered.

Canberra: zoning is already cultural but rarely fully done

The ACT runs the highest heating load in the country. A typical 4-bedroom gas-heated Canberra household burns around 55 GJ of gas a year on space heating, at the ACT gas rate of $0.041/MJ. That is about $2,250 a year on heating fuel alone, with roughly $1,690 falling in the winter quarter. The winters are genuinely cold and most houses have full central heating, so households in Canberra already do more zone-closing than the rest of the country by instinct.

The remaining inefficiency in Canberra is that the central heating still runs even when only the living room is occupied, because the thermostat reads a single hallway location and the ducts are not properly dampered. A full retrofit of zoning dampers is a $2,000-ish job that pays back within two winters for a typical Canberra household. For those not ready to do that, the cheapest equivalent is to physically close half the registers and drop the thermostat. Around $500 a winter quarter saved off the $1,690 with zero hardware.

The escape hatch: a $2,500 reverse-cycle split in one room

If you read everything above and the answer was “the central gas heating is the actual problem, not how I am using it,” there is one move that fits in the six-week window before the big bills land: install a single reverse-cycle split in your main living room.

A 5–7 kW unit costs $2,000 to $3,500 installed, takes one to two weeks of lead time, and about half a day to fit. Used exclusively in the one room and with the central gas heating switched off, a Melbourne household typically sees the winter heating cost drop from around $1,170 (gas-ducted everywhere) to around $280 (electric reverse cycle in one room only, COP 3.5). That is around $890 saved in the first winterand pays a $2,500 unit off in just under three years on heating savings alone, with the cooling capacity thrown in for summer.

The reverse-cycle unit also runs as air conditioning in summer. If you would have bought one anyway in the next three years, buying it now and using it as your one-room heater this winter is the cheapest version of that decision. For the deeper math on switching central heating entirely, see our reverse cycle vs gas heating post.

If you live in QLD, NT, or northern WA

Heating is not your June bill problem. The spike you see in June and July is hot water (cooler tap water and longer showers) plus standby load that compounds when you stop using outdoor spaces and rooms stay closed. The action list flips:

• Replace gas or resistance-electric hot water with a heat-pump hot water system. Single biggest move for a warm-climate household and a four to ten year payback. See our heat pump vs gas hot water post.
• Audit standby load. A four-bedroom Brisbane house typically has 60 to 100W of standby draw running 24/7: that is around $250 a year at QLD rates, much of it from old TVs, set-top boxes, and PC peripherals nobody uses. Smart power strips fix it.
• Shorter showers and a flow restrictor. Cool tap water in winter makes the gas or electric hot water work harder for every minute the tap is open.

The 6-week checklist

If the next quarter bill is the deadline, do these in order:

1. This week: drop the thermostat two degrees, close the doors to unused rooms, and ring your retailer to ask for a time-of-use tariff if you are not on one.
2. Next two weeks: $30 of door snakes and weatherstrip on the doors between heated and unheated rooms. Pull the heavy curtains closed at sunset every day.
3. Weeks three to six: if you are an owner and your ceiling insulation is below R3, book the top-up. Alternatively, if you have decided the central heating is going, book a reverse-cycle split for the living room. Both of these can be done inside the window before the late-July bill lands.

A couple of caveats

The time-of-use switch only works if you have a smart meter. Most cool-state houses now do; if yours is still an old accumulation meter, ask the retailer to swap it (free in most states) and the ToU plan can follow.

Some retailers charge an early-exit fee on flat-rate contracts. Worth a five-minute phone call before you sign anything, but typically the fee is $50 to $80 and the new tariff covers it inside a month.

Winter weather varies year-to-year. The numbers in this post assume an average Australian winter; a cold snap can push them 10 to 20 percent higher and a mild winter pulls them back. The relative ranking of the interventions does not change.

Run your own numbers

The figures above are for a typical 4-bedroom household at average rates. Your bill depends on your actual heating system, occupancy pattern, retail tariff, and how cold your particular winter ends up being. The calculator works out the exact numbers for your postcode and household, and shows where heating-quality interventions fit in the optimal sequence of upgrades for your situation.

Where these numbers come from

Per-state appliance energy consumption from the Australian and New Zealand Residential Baseline Study 2021. Electricity and gas rates from Canstar and AER 2025-26 averages. Reverse-cycle split-system install costs from SolarChoice and installer surveys. Insulation costs from Sustainability Victoria and ServiceSeeking quotes. Full data source list on the data sources page.