Gas Hot Water System Replacement Cost in Australia: What Affects the Price?

Oct 3, 2024

The cost to replace a gas hot water system in Australia depends on the system type, brand, gas connection, installation requirements and whether you are replacing like-for-like or changing to a different style of unit.

A straightforward gas hot water replacement is usually cheaper than a major upgrade, relocation or conversion. A like-for-like swap from an existing gas storage unit to a similar gas storage model is generally simpler than changing from electric to gas, moving the unit, upgrading pipework or switching to a larger instant gas system.

Installed Today offers gas hot water systems for customers comparing replacement options online. Supply-only ordering is available across major Australian metro areas, while selected supplied-and-installed options are available on eligible products in Brisbane and Gold Coast service areas where shown.

Quick Answer

Gas hot water system replacement cost can vary widely because the product price is only one part of the total job.

The final cost can be affected by:

The brand and model you choose
Whether the unit is gas storage or instant gas
Natural gas or LPG connection
System size and household demand
Existing pipework and gas supply
Water pressure
Access to the installation location
Whether new valves or compliance upgrades are required
Whether the old system needs removal or disposal
Whether the replacement is like-for-like or a system change

For supply-only products, the listed product price generally covers the hot water unit only. It does not usually include installation labour, plumbing changes, gas work, electrical work, new valves, pipework changes, removal of the old unit or compliance upgrades unless those items are clearly selected or included.

What Is a Gas Hot Water System?

A gas hot water system uses natural gas or LPG to heat water for showers, taps, kitchens and laundries. In Australian homes, gas hot water systems usually fall into two main categories:

Gas storage hot water systems
Instant gas hot water systems

A gas storage system keeps hot water in a tank and reheats it as needed. An instant gas system, also called continuous flow, heats water when a hot tap is turned on.

Customers comparing hot water systems should also consider electric storage, heat pump, instant electric and solar hot water, because the best option depends on the property, energy source and usage pattern.

Main Factors That Affect Gas Hot Water Replacement Cost

1. Gas Storage vs Instant Gas

The type of system you choose has a major impact on cost.

A gas storage system is often chosen when the home already has a similar gas storage unit and the customer wants a straightforward replacement. Common options include 130L and 135L gas hot water systems and 160L and 170L gas hot water systems.

An instant gas system can be a good option where space is limited or where the household wants continuous flow hot water instead of a storage tank. Popular sizes include 16L, 20L and 26L models. You can compare options in the instant gas hot water systems collection.

Changing from gas storage to instant gas may involve extra checks, including gas pipe sizing, water pressure and wall mounting location.

2. Natural Gas vs LPG

Natural gas and LPG are not interchangeable. A natural gas hot water system must be connected to natural gas, while an LPG hot water system must be connected to LPG.

Choosing the wrong gas type can create safety and compliance problems, so this should be checked before ordering. Gas work must be completed by a licensed gas fitter.

For example, customers comparing 26L units should choose the correct gas type, such as a Rinnai Infinity B26 Natural Gas Hot Water System, Rinnai Infinity B26 LPG Gas Hot Water System, Rheem 26L Natural Gas Hot Water System or Rheem 26L LPG Gas Hot Water System.

3. Brand and Model

Brand and model affect the product price, features, warranty terms, efficiency rating and long-term suitability.

Common gas hot water brands include Rheem hot water systems, Rinnai hot water systems, Vulcan hot water systems and Bosch hot water systems.

A basic replacement model may suit a simple like-for-like job, while a larger or higher-feature system may suit homes with higher demand, multiple bathrooms or more frequent hot water use.

4. Size and Household Demand

The right gas hot water system size depends on how the home uses hot water.

Key things to consider include:

Number of people in the home
Number of bathrooms
Shower length and frequency
Whether multiple showers run at once
Bath use
Kitchen and laundry use
Existing system performance
Whether the old unit regularly ran out of hot water

For gas storage, the tank size matters. For instant gas, the litres-per-minute rating matters. A 16L unit may suit lower-demand homes, while 20L or 26L systems may suit larger households or homes with higher simultaneous use.

However, bigger is not automatically better. For 26L instant gas hot water systems, gas pipe sizing and water pressure must be suitable. Multiple outlets can still exceed the capacity of a system if demand is too high at the same time.

5. Installation Complexity

A simple replacement is usually more affordable than a complex job.

A replacement may cost more when:

The new system is being relocated
The gas pipe needs upgrading
Water pipework needs changing
Valves need replacing
Access is difficult
The old unit is non-compliant
The old unit needs removal and disposal
Drainage changes are required
The system type is changing
Electrical work is required
The home is switching from electric to gas

Licensed trades should confirm what is required before a supply-only product is ordered.

6. Existing Gas Connection

If the home already has the right gas connection in the right location, the job may be simpler. If the home does not have gas available, or if the existing supply is not suitable for the new unit, costs can increase.

This is especially important when upgrading to larger instant gas units. A 26L system can require more gas flow than a smaller unit, so gas pipe sizing should be checked by a licensed gas fitter before ordering.

7. Water Pressure and Pipework

Water pressure affects the performance of instant gas systems. If water pressure is too low, restricted or inconsistent, the system may not perform as expected.

Before ordering, it is worth considering:

Existing water pressure
Pipe size
Distance from the meter or supply
Pressure limiting valves
Filters or restrictions
Simultaneous outlet use
Shower and tap flow rates

Plumbing work should be completed by a licensed plumber where required.

Gas Storage vs Instant Gas: Which Costs More?

There is no single answer because the cheaper option depends on the existing setup.

Gas Storage Hot Water Systems

Gas storage systems can suit homes that already have a similar storage unit and want a familiar replacement.

Common examples include:

Gas storage may be a practical option where the home has suitable space for the tank and the existing setup is already compliant.

Instant Gas Hot Water Systems

Instant gas systems heat water on demand and are wall-mounted, which can save ground space compared with storage tanks.

Common options include:

Instant gas can be a good fit where the home has suitable gas supply, water pressure, outdoor wall space and installation access. External gas continuous flow units are designed for outdoor installation unless the specific model is approved for internal flued installation.

Is a 26L Gas Hot Water System Worth It?

A 26L instant gas hot water system is popular for larger households, but it is not automatically the right choice for every home.

A 26L system may suit homes with:

Higher hot water demand
Multiple bathrooms
Longer shower use
More frequent simultaneous hot water use
Suitable gas supply
Suitable water pressure
Outdoor wall space for an external unit

Before ordering a 26L model, check whether the property has suitable gas pipe sizing and water pressure. A larger system may not perform properly if the gas supply or water pressure is not suitable.

You can compare options in the 26L instant gas hot water systems range.

Should You Replace Like-for-Like?

A like-for-like replacement can be simpler when the old unit size, gas type, location and connections are still suitable.

However, replacing the same model or size is not always the best choice. You may need to rethink the system if:

The old unit regularly ran out of hot water
The household has grown
Bathrooms have been added
Shower habits have changed
The home now uses more hot water at once
The old location is no longer suitable
The old setup is not compliant
You want to change from storage to instant gas

Customers unsure whether gas is still the best option can also compare electric hot water systems, heat pump hot water systems and instant electric hot water systems.

Supply-Only vs Supplied-and-Installed

Installed Today offers supply-only ordering across major Australian metro areas. This can suit customers who already have a licensed installer organised and want to order the product online.

Selected supplied-and-installed options are available on eligible products in Brisbane and Gold Coast service areas. Availability depends on the product, address and installation requirements.

For supply-only products, the listed product price generally covers the product only.

It does not usually include:

Installation labour
Plumbing alterations
Electrical work
Gas work
New valves
Pipework changes
Gas pipe upgrades
Drainage changes
Tempering valve upgrades
Pressure limiting valve upgrades
Expansion control valves
Old unit removal
Disposal
Compliance upgrades
Concrete bases or slab work
Flue kits unless listed
Temperature controllers unless listed
Relocation of the system
Rebate administration
Site assessment

Always confirm installation requirements with a licensed installer before ordering a supply-only gas hot water system.

Brisbane and Gold Coast Replacement Considerations

In Brisbane and Gold Coast homes, gas hot water replacement can vary depending on the property type, age and access.

Older homes may have different pipework, valve layouts or installation clearances compared with newer builds. Townhouses and tight side access areas can also affect installation complexity. Coastal areas may need extra attention to system location and exposure.

For selected eligible products, supplied-and-installed options may be available in Brisbane and Gold Coast service areas where shown. Customers outside those areas, or customers who already have a tradesperson, may prefer supply-only ordering.

Are Rebates Available for Gas Hot Water Systems?

Rebates, STCs and incentives can change over time and may depend on the state, product type, installation details and eligibility rules.

Gas hot water systems are not automatically eligible for rebates. Heat pump and solar hot water incentives may be available in some situations, but customers should confirm current eligibility before relying on any rebate or incentive.

Do not choose a hot water system based only on a possible rebate. The right system should suit the home, energy source, household demand, installation location and long-term use.

Common Mistakes When Replacing a Gas Hot Water System

Choosing the Wrong Gas Type

Natural gas and LPG are different. Ordering the wrong gas type can delay the job and create safety issues.

Assuming Bigger Is Always Better

A larger instant gas system may not perform correctly if the gas pipe sizing or water pressure is not suitable.

Ignoring Installation Extras

The product price may not include valves, pipework, gas upgrades, drainage changes, disposal or compliance work.

Replacing the Same Size Without Checking Usage

If the old system struggled to keep up, replacing it with the same size may repeat the same problem.

Buying Before Installer Confirmation

Supply-only ordering works best when a licensed installer has confirmed the model, gas type, location and installation requirements.

Before Ordering Checklist

Before ordering a gas hot water system, check:

Is the home connected to natural gas or LPG?
Is the replacement gas type correct?
Is the system gas storage or instant gas?
Is the size suitable for the household?
Is the existing location compliant?
Is outdoor installation suitable for an external gas unit?
Is gas pipe sizing suitable for the selected unit?
Is water pressure suitable, especially for instant gas?
Are new valves or compliance upgrades likely?
Is old unit removal included or separate?
Is the product supply-only or supplied-and-installed?
Has a licensed installer confirmed the product is suitable?

Frequently Asked Questions

How much does it cost to replace a gas hot water system?

Gas hot water replacement cost depends on the unit, gas type, installation complexity, access, pipework, valves and whether the job is like-for-like or a system change. The product price alone does not usually represent the full installed cost unless supplied-and-installed inclusions are clearly selected or shown.

Is instant gas cheaper than gas storage?

Not always. Instant gas may be compact and efficient, but changing from storage to instant gas can involve extra checks such as gas pipe sizing, water pressure and mounting location. Gas storage may be simpler where the home already has a similar compliant setup.

What size gas hot water system do I need?

The right size depends on household size, bathrooms, shower habits and simultaneous hot water use. For instant gas, 16L, 20L and 26L are common sizes. For gas storage, 135L and 170L options are common. A licensed installer can help confirm suitability.

Can I replace a natural gas unit with an LPG unit?

Only if the property is set up for LPG and the system is the correct LPG model. Natural gas and LPG are not interchangeable. Gas work must be completed by a licensed gas fitter.

Are 26L instant gas systems suitable for every home?

No. A 26L system may suit higher-demand homes, but gas pipe sizing and water pressure must be suitable. Bigger is not automatically better, and multiple outlets can still exceed system capacity.

Can I install a gas hot water system myself?

No. Gas hot water installation involves licensed gas fitting and plumbing work. Electrical work may also be required in some situations. Use licensed trades where required.

Does supply-only pricing include installation?

No. Supply-only pricing generally covers the product only. It does not usually include installation labour, gas work, plumbing changes, valves, disposal, pipework changes or compliance upgrades unless clearly listed.

Final Word

Gas hot water system replacement cost depends on more than the unit price. The best replacement choice comes down to gas type, household demand, system size, access, pipework, water pressure and whether the job is a simple like-for-like replacement or a more complex upgrade.

Installed Today makes it easy to compare gas hot water systems, instant gas hot water systems and 26L instant gas hot water systems online.

For supply-only orders, confirm the system with your licensed installer before purchasing. For eligible Brisbane and Gold Coast products, check whether a supplied-and-installed option is available where shown.

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