Running costs are a key consideration for Melbourne homeowners with gas ducted heating — the heating system that will dominate the household’s gas bill for five to six months of the year. Understanding how star rating, zoning, and maintenance affect gas consumption helps Melbourne households reduce costs without sacrificing winter comfort. This guide provides Melbourne 2025 gas cost modelling and practical guidance on reducing heating bills.
Gas Consumption and Melbourne Rates
Melbourne’s residential gas network is supplied by AusNet Gas and Multinet Gas. The usage rate for residential gas in Melbourne in 2025 is approximately 3.4 to 3.8 cents per MJ (megajoule), depending on the retailer and plan. The daily supply charge is approximately $0.80 to $0.90 per day, representing a fixed annual cost of approximately $295 to $330 before any gas is consumed.
Ducted heaters are rated by their gas input in MJ/h and their thermal efficiency (star rating). The actual gas consumed per hour of operation is: Input MJ/h ÷ thermal efficiency. For a 5-star (91% efficiency) 25 MJ/h heater: 25 ÷ 0.91 = 27.5 MJ/h actual gas consumption.
| Heater Size / Rating | Gas Input | Efficiency | Gas Use per Hour | Cost per Hour (3.6¢/MJ) |
|---|---|---|---|---|
| Small home, 6-star | 15 MJ/h | 95% | 15.8 MJ | $0.57 |
| Medium home, 5-star | 25 MJ/h | 91% | 27.5 MJ | $0.99 |
| Medium home, 3-star (older) | 25 MJ/h | 72% | 34.7 MJ | $1.25 |
| Large home, 6-star | 40 MJ/h | 95% | 42.1 MJ | $1.52 |
| Old 2-star heater | 30 MJ/h | 60% | 50.0 MJ | $1.80 |
How Star Rating Affects Running Costs
The energy star rating of a Melbourne gas ducted heater directly determines how much gas it consumes per unit of heat delivered. The rating system runs from 1 star (approximately 55 to 60 per cent thermal efficiency) to 6 stars (approximately 95 to 97 per cent). Modern Brivis and Rinnai top-of-range models achieve 6 stars.
Seasonal cost comparison — medium Melbourne home, 90 heating days, 6 hours per day average run time:
| Star Rating | Efficiency | Seasonal Gas Use | Seasonal Gas Cost | Annual Saving vs 2-star |
|---|---|---|---|---|
| 2-star (older Melbourne heater) | 60% | 27,000 MJ | $972 | — |
| 3-star | 72% | 22,500 MJ | $810 | $162 |
| 5-star | 91% | 17,800 MJ | $641 | $331 |
| 6-star | 95% | 17,000 MJ | $612 | $360 |
Replacing a 2-star heater with a 6-star model in a medium Melbourne home saves approximately $360 per year in gas costs — this saving contributes materially to the payback calculation when a replacement heater is being considered. See our guide on when to replace your Melbourne heater.
Total Seasonal Cost Model
Full annual cost of ownership for a Melbourne gas ducted heater (medium home, 5-star heater, average usage):
| Cost Category | Annual Cost (AUD) | Notes |
|---|---|---|
| Gas usage (heating only) | $560–$700 | 5-star heater, 90-day season, 6 hrs/day |
| Gas supply charge | $295–$330 | Fixed daily charge regardless of usage |
| Annual service | $300–$450 | Complete professional service |
| Filter replacement | $20–$50 | DIY at hardware store |
| Total annual cost | $1,175–$1,530 | Medium Melbourne home |
How Zoning Reduces Heating Costs
Ducted heating zone control allows Melbourne homeowners to heat only the rooms in use, significantly reducing gas consumption. A Melbourne home with four bedrooms and two living areas running the system on whole-home operation for six hours per day uses the heater’s full rated capacity. Closing off three unused bedrooms during the daytime reduces the heated floor area by approximately 40 per cent — the heater satisfies the reduced space faster, cycles off sooner, and runs for less total time per day.
Zone savings depend on: the proportion of the home that is zoned off; the heater’s ability to manage reduced duct pressure (modern variable-speed blowers handle this better than older single-speed units); and the effectiveness of the damper seals in unused zones. A well-commissioned zone system on a modern variable-speed Brivis or Rinnai unit can realistically achieve 25 to 35 per cent gas savings compared to whole-home operation.
See our Melbourne ducted heating zones guide for zone setup, fault diagnosis, and optimisation.
How to Reduce Ducted Heating Costs
- Keep the filter clean: a blocked filter makes the heater work harder for less output — check and clean monthly during Melbourne’s heating season. See our filter replacement guide.
- Annual service: a correctly tuned burner and clean heat exchanger operate at rated efficiency; a dirty system loses efficiency progressively. From $300.
- Use the thermostat accurately: set to 18 to 21°C during occupied periods. Each degree above 21°C adds approximately 8 to 10 per cent to heating costs in Melbourne conditions.
- Zone off unoccupied rooms: close off bedrooms during the day and living areas after occupants go to bed. See our zones guide.
- Draught-seal the home: in Melbourne’s established brick homes, draughts around doors and windows account for a significant proportion of heat loss. Draught sealing (door seals, gap foam) is low-cost and directly reduces heating run time.
- Ceiling insulation: if your Melbourne home lacks adequate ceiling insulation (or has degraded old glasswool), upgrading to R3.5 or above significantly reduces heat loss through the ceiling — the primary pathway for heat loss in Melbourne’s brick homes.