Gas Water Heating System: Storage vs Instant Gas Hot Water Buying Guide

Oct 9, 2024

A gas water heating system uses natural gas or LPG to heat household hot water for showers, baths, kitchen use and laundry. For many homes, gas hot water can be a practical option where the property already has a suitable gas supply, outdoor installation location and household demand that matches the system.

The two main gas hot water options are gas storage and instant gas hot water. Gas storage systems heat and store water in a tank. Instant gas systems, also called continuous flow systems, heat water as it passes through the unit.

The right choice depends on your household size, number of bathrooms, shower habits, gas type, water pressure, gas pipe sizing, installation location and whether you want supply only or an eligible supplied-and-installed option.

Installed Today makes it easy to compare and order gas hot water systems, instant gas hot water systems, 26L instant gas hot water systems and hot water systems online, with supply-only ordering available across major Australian metro areas and selected supplied-and-installed options available on eligible products in Brisbane and Gold Coast service areas.

Quick Answer: What Is the Best Gas Water Heating System?

The best gas water heating system is the one that matches your gas supply, hot water demand and installation conditions.

As a general guide:

Gas storage hot water systems can suit homes that want stored hot water ready for use
Instant gas hot water systems can suit homes wanting continuous flow hot water without a large tank
26L instant gas systems are often compared for larger households and higher shower demand
20L instant gas systems may suit smaller-to-medium households
16L instant gas systems may suit lower-demand homes or compact applications
Natural gas and LPG systems are not interchangeable
Gas work must be completed by a licensed gas fitter
Gas pipe sizing and water pressure must support larger instant gas units

Before ordering supply only, confirm the gas type, model, size, water pressure, gas pipe sizing, outdoor location, valves, drainage, access and installation suitability with your licensed installer.

What Is a Gas Water Heating System?

A gas water heating system heats water using natural gas or LPG. The heated water is then supplied to showers, baths, kitchen taps, laundry fixtures and other hot water outlets around the home.

Gas hot water systems are commonly used where the home already has:

Natural gas connected to the property
LPG bottles or cylinders
Outdoor space for a gas hot water unit
Suitable gas pipework
Suitable water pressure
Hot water demand that matches gas system performance

Gas hot water systems are different from electric hot water systems, which use an electric element, and heat pump hot water systems, which use heat from the surrounding air to help heat stored water.

Natural Gas vs LPG Gas Hot Water

This is the most important check before ordering any gas water heating system.

Natural gas and LPG are different fuels. A natural gas hot water system must not be treated as interchangeable with an LPG hot water system.

Natural gas is supplied through a gas network connection
LPG is supplied through gas bottles or cylinders
Natural gas models and LPG models are different
Any approved conversion must be completed by a licensed gas fitter and only where the manufacturer allows it
Ordering the wrong gas type can make the unit unsuitable for your property

Installed Today lists natural gas and LPG models separately where available, including options such as the Rinnai Infinity B26 Natural Gas Hot Water System, Rinnai Infinity B26 LPG Gas Hot Water System, Rheem 26L Natural Gas Hot Water System and Rheem 26L LPG Gas Hot Water System.

How Gas Water Heaters Work

Gas water heaters use a burner to heat water. The way they do this depends on whether the system is a storage unit or an instant gas unit.

Gas Storage Hot Water

A gas storage system heats water inside a tank and stores it ready for use. When hot water is used, cold water refills the tank and the gas burner reheats the water.

This style can suit homes that prefer stored hot water and already have space for a gas storage tank.

Instant Gas Hot Water

An instant gas hot water system heats water only when a hot tap is turned on.

The basic process is:

A hot tap or shower is turned on
Water flow is detected by the unit
The gas burner activates
Water passes through a heat exchanger
Hot water flows to the fixture
The burner turns off when hot water demand stops

This is why instant gas systems are also called continuous flow hot water systems or tankless gas hot water systems.

Main Types of Gas Water Heating Systems

Gas Storage Hot Water Systems

Gas hot water systems include storage and instant gas options. Gas storage systems heat and store water in a tank.

Gas storage may suit homes that:

Already have natural gas or LPG
Want stored hot water
Prefer a tank-style replacement
Have suitable outdoor installation space
Want fast recovery compared with some electric storage setups
Have household usage that suits stored hot water

Common gas storage categories include:

Product examples include:

Instant Gas Water Heating Systems

Instant gas hot water systems heat water as it passes through the unit. They do not store a full tank of hot water.

Instant gas may suit homes that:

Want continuous flow hot water
Want to save space compared with a storage tank
Have suitable natural gas or LPG
Have enough water pressure
Have suitable gas pipe sizing
Have suitable outdoor wall space
Want to compare 16L, 20L and 26L options

Instant gas systems are commonly compared by litres per minute. Larger households often compare 26L instant gas hot water systems, but a 26L unit only performs correctly where the gas supply and water pressure support it.

Popular instant gas options include:

External gas hot water units are designed for outdoor installation unless the specific manufacturer model is approved for internal flued installation.

Gas Storage vs Instant Gas Hot Water

Gas storage and instant gas hot water systems both use gas, but they work differently.

Gas System Type	How It Works	Best Suited To	Key Checks
Gas storage	Heats and stores water in a tank	Homes wanting stored hot water and familiar replacement style	Tank size, gas type, outdoor location, valves, drainage
Instant gas	Heats water as it flows through the unit	Homes wanting continuous flow hot water and compact wall-mounted design	Flow rate, gas pipe sizing, water pressure, gas type
26L instant gas	Larger continuous flow option	Some family homes and higher-demand households	Gas supply and water pressure must support the unit

A storage system may be better if you want a tank-style setup and your old gas storage system worked well.

Instant gas may be better if you want continuous flow hot water and the property has suitable gas pipe sizing, water pressure and outdoor wall space.

What Size Gas Water Heating System Do You Need?

The right size depends on household demand, not just the old unit size.

Consider:

Number of people in the home
Number of bathrooms
Shower length
Bath use
Kitchen and laundry use
Whether multiple showers run at once
Morning and evening peak demand
Existing system type
Existing system size
Whether the old system ran out of hot water
Natural gas or LPG availability
Gas pipe sizing
Water pressure
Outdoor installation location
Distance from the unit to fixtures

For gas storage, many homes compare 130/135L and 160/170L categories.

For instant gas, common sizes include 16L, 20L and 26L.

Do not choose a larger system automatically. A larger instant gas unit will not perform properly if the gas supply or water pressure is unsuitable.

16L Gas Water Heating Systems

A 16L instant gas hot water system may suit smaller homes, lower-demand households or compact applications.

It may be considered for:

Smaller homes
One-bathroom homes
Lower shower demand
Replacing an existing 16L continuous flow unit
Properties where gas supply or water pressure does not support a larger unit

Relevant options include:

20L Gas Water Heating Systems

A 20L instant gas hot water system may suit small-to-medium households with moderate hot water demand.

It may suit:

Smaller families
Moderate shower use
One-to-two bathroom homes, depending on fixtures and habits
Replacing an existing 20L unit
Homes where a 26L unit is not needed or not supported by the site

Relevant options include:

26L Gas Water Heating Systems

A 26L instant gas hot water system is often compared for larger households and higher hot water demand.

It may suit:

Family homes
Higher shower demand
Some two-bathroom homes
Larger households
Homes replacing an older continuous flow unit
Properties where gas supply and water pressure support the system

Relevant options include:

For 26L systems, gas pipe sizing and water pressure are critical. A licensed gas fitter should confirm suitability before ordering.

Gas Water Heating vs Electric Hot Water

Gas and electric hot water systems suit different homes.

Electric hot water systems may suit homes without gas or customers wanting a straightforward electric storage replacement.

Gas water heating may suit homes already set up for natural gas or LPG.

Option	Best Suited To	Key Considerations
Gas storage	Homes with gas wanting stored hot water	Correct gas type, outdoor location and tank size
Instant gas	Homes wanting continuous flow gas hot water	Gas pipe sizing, water pressure and gas type
Electric storage	Homes without gas or simple replacements	Tank size, tariff, electrical supply and running costs
Heat pump	Energy-focused electric homes	Outdoor airflow, drainage, access and noise placement

If your home has no gas, electric storage or heat pump hot water may be more relevant.

Gas Water Heating vs Heat Pump Hot Water

A gas water heating system and a heat pump hot water system can both suit different homes.

Gas may suit homes that:

Already have natural gas or LPG
Want gas storage or instant gas hot water
Have suitable outdoor installation space
Have suitable gas pipe sizing and water pressure
Prefer continuous flow hot water

Heat pump hot water may suit homes that:

Want an electric hot water upgrade
Are replacing older electric storage
Have suitable outdoor space
Have good airflow
Can manage condensate drainage
Want to pair hot water operation with rooftop solar where timing suits

A heat pump is not automatically better than gas, and gas is not automatically better than a heat pump. The right choice depends on the home.

Gas Water Heating vs Solar Hot Water

Solar hot water systems use roof-mounted collectors to capture heat from the sun and usually include an electric or gas booster.

Solar hot water may suit homes with:

Suitable roof space
Strong sun exposure
Minimal shading
Suitable booster setup
Long-term energy efficiency goals

Gas water heating may suit homes that already have gas and want a storage or instant gas system without roof-mounted collectors.

For some homes, a heat pump may be easier to compare than solar hot water where roof space, shading or roof access is an issue.

Benefits of Gas Water Heating Systems

Fast Hot Water Recovery

Gas storage systems can reheat stored water faster than some electric storage setups, depending on the model and household demand.

Continuous Flow Options

Instant gas systems can provide continuous flow hot water where the system is correctly sized and the property supports it.

Compact Wall-Mounted Instant Gas Units

Instant gas systems are usually compact and wall-mounted outside, which can free up space compared with a storage tank.

Natural Gas or LPG Options

Gas hot water systems are available in natural gas and LPG models, making them suitable for different property types where the correct model is selected.

Familiar Replacement Pathway

Many homes already have gas hot water. Replacing with a similar gas system may be practical where the old system worked well and the setup still suits.

Limitations of Gas Water Heating Systems

Gas hot water is not right for every home.

Potential limitations include:

Natural gas and LPG models are not interchangeable
Gas work requires a licensed gas fitter
Gas pipe sizing may need checking
Water pressure must support instant gas units
Outdoor location and clearances matter
External gas units must not be installed indoors unless approved as internal flued models
Installation costs can change if pipework, valves or drainage need upgrading
LPG bottle supply and running cost should be considered where relevant
Future household energy preferences may favour electric or heat pump options

The system must suit the property, not just the household size.

Installation Requirements for Gas Water Heating Systems

Before ordering a gas hot water system, your installer should check:

Natural gas or LPG supply
Correct gas type
Existing system type
Existing system size
Household hot water demand
Gas pipe sizing
Water pressure
Water flow rate
Outdoor installation location
Required clearances
Ventilation and flue requirements where applicable
Electrical requirements for ignition or controls where relevant
Pipework route
Access for future servicing
Existing valves and compliance requirements
Drainage and overflow requirements
Whether old unit removal and disposal are needed

Gas work must be completed by a licensed gas fitter.

Outdoor and Indoor Gas Hot Water Suitability

Most external gas hot water units are designed for outdoor installation.

Do not install an external gas hot water unit indoors unless the specific manufacturer model is designed and approved for internal flued installation.

Before ordering, confirm:

Whether the unit is external or internal flued
Wall clearances
Window and door clearances
Ventilation requirements
Flue requirements where applicable
Access for service
Weather exposure
Pipework route
Gas supply route

This is especially important when replacing an old indoor or semi-enclosed system.

What Is Not Included in Supply-Only Gas Hot Water Pricing?

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

It does not usually include:

Installation labour
Licensed gas fitting
Electrical 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
Relocation of the system
Flue kits or extra accessories unless listed
Gas type conversion

Always check the product page and confirm full site requirements with your licensed installer before ordering.

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 gas fitter or installer organised and want to order the product online.

Supply-only may suit you if:

Your installer has confirmed the correct model
The correct gas type has been selected
Gas pipe sizing has been checked
Water pressure has been checked
Outdoor location and clearances are suitable
Access and drainage are suitable
You understand what is not included in the product price

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.

Brisbane and Gold Coast Gas Hot Water Considerations

For Brisbane and Gold Coast homes, gas hot water selection often depends on existing system type, outdoor space, natural gas or LPG availability and access.

Common local considerations include:

Natural gas vs LPG availability
Older gas storage replacements
Homes changing from gas storage to instant gas
Outdoor wall space for continuous flow units
Gas pipe sizing for 26L systems
Water pressure
Side access
Drainage and overflow points
Existing valve condition
Distance to bathrooms and kitchen
Whether heat pump or electric storage may suit better

Installed Today offers supply-only ordering across major Australian metro areas, with selected supplied-and-installed options available on eligible products in Brisbane and Gold Coast service areas.

Gas Hot Water Brands to Compare

Installed Today stocks a range of major hot water brands, including:

For instant gas, Rinnai, Rheem and Bosch are commonly compared across different sizes and gas types.

Brand matters, but the correct gas type, system size, water pressure, pipe sizing and installation suitability matter more than brand alone.

Rinnai Gas Water Heating Systems

Rinnai hot water systems are commonly compared for instant gas and electric hot water options.

Popular Rinnai gas options include:

Rinnai instant gas systems may suit homes wanting continuous flow hot water where gas supply and water pressure support the selected model.

Rheem Gas Water Heating Systems

Rheem hot water systems include electric, gas and heat pump options.

Rheem gas options include storage and instant gas systems such as:

Rheem may be worth comparing if you want both gas storage and instant gas options from a major brand.

Bosch Gas Water Heating Systems

Bosch hot water systems are commonly compared for compact instant gas hot water options.

Relevant Bosch gas options include:

Bosch may suit some lower-demand gas hot water applications, depending on gas type, water pressure and household use.

Common Gas Water Heating Problems to Watch For

A gas hot water system may need attention if you notice:

Hot water running out too quickly
Hot water temperature changing suddenly
Pilot or ignition issues
System not starting
Unusual noises
Rust or corrosion
Leaks around the system
Discoloured hot water
Gas smell
Poor flow from hot taps
Error codes on instant gas units

Gas smell or suspected gas leaks should be treated seriously. Turn off gas where safe to do so and contact a licensed gas fitter or relevant emergency service.

Do not attempt gas repairs yourself.

Maintenance for Gas Water Heating Systems

Gas hot water systems need maintenance according to manufacturer instructions and local requirements.

General maintenance may include:

Keeping the area around the unit clear
Checking for visible leaks
Watching for rust or corrosion
Checking valves where required
Keeping external units clear of debris
Checking for unusual noises
Monitoring temperature consistency
Arranging licensed gas checks where required
Following manufacturer servicing guidance

Gas servicing and repairs should be handled by licensed trades.

Common Mistakes When Choosing Gas Water Heating

Ordering the Wrong Gas Type

Natural gas and LPG units are different. Always select the correct model.

Choosing 26L Instant Gas Without Checking Gas Pipe Sizing

A 26L unit can suit some family homes, but only if the gas supply and water pressure support it.

Replacing the Same System Without Checking Demand

If the old gas system ran out of hot water or struggled at peak times, replacing it with the same size may repeat the issue.

Installing an External Gas Unit Indoors

External gas units are outdoor units unless the specific model is designed and approved for internal flued installation.

Comparing Supply-Only and Installed Prices Incorrectly

A product-only price is not the same as a full installed price.

Forgetting About Valves and Drainage

Replacement may involve valves, overflow, drainage or compliance upgrades.

Choosing by Brand Alone

Brand matters, but the right gas type, size, pipework and water pressure matter more.

Before Ordering Checklist

Before ordering a gas water heating system, confirm:

Current system type
Current system size
Whether the old system ran out of hot water
Number of people in the home
Number of bathrooms
Shower habits
Peak hot water demand
Natural gas or LPG availability
Correct gas type
Gas pipe sizing
Water pressure
Outdoor installation location
External or internal flued suitability
Access for delivery and installation
Drainage and overflow requirements
Whether new valves may be needed
Whether electrical connection is required
Whether removal and disposal are included
Whether supply-only or supplied-and-installed is the right option
Installer confirmation before buying supply only

Frequently Asked Questions

What is a gas water heating system?

A gas water heating system uses natural gas or LPG to heat water for showers, kitchen use, laundry and household hot water needs. It may be a storage system or an instant gas system.

Is gas hot water better than electric?

It depends on the home. Gas can suit properties already set up for natural gas or LPG. Electric storage can suit homes without gas, while heat pumps may suit energy-focused homes with suitable outdoor space.

What is the difference between gas storage and instant gas hot water?

Gas storage systems heat and store water in a tank. Instant gas systems heat water as it flows through the unit and do not store a full tank of hot water.

What size gas water heater do I need?

The right size depends on household size, bathrooms, shower habits, gas type, water pressure and whether you want storage or instant gas. Common instant gas sizes include 16L, 20L and 26L.

Is a 26L gas hot water system good for a family?

A 26L instant gas system can suit some family homes, but only where gas pipe sizing and water pressure support the unit. A licensed gas fitter should confirm suitability.

Can I use LPG with a natural gas hot water system?

No. Natural gas and LPG systems are different. They are not interchangeable unless the manufacturer allows an approved conversion by a licensed gas fitter.

Can an external gas hot water unit be installed indoors?

No. External gas units are designed for outdoor installation unless the specific model is approved for internal flued installation.

Does gas hot water need electricity?

Some gas hot water systems need electricity for ignition, controls or operation. Check the specific model and installation requirements before ordering.

Can I install a gas water heater myself?

No. Gas hot water systems involve plumbing, gas fitting, water pressure, valves and compliance requirements. Gas work must be completed by a licensed gas fitter.

What is not included in supply-only gas hot water pricing?

Supply-only pricing generally excludes installation, gas fitting, electrical work, valves, pipework changes, gas pipe upgrades, drainage, old unit removal, disposal and compliance upgrades unless selected or clearly shown.

Final Word

A gas water heating system can be a practical choice for homes with suitable natural gas or LPG. Gas storage systems can suit households wanting stored hot water, while instant gas systems can suit homes wanting continuous flow hot water and a compact outdoor unit.

The best gas hot water system is not just the cheapest or biggest model. It is the system that matches your household demand, correct gas type, water pressure, gas pipe sizing, outdoor location and installation requirements.

Before ordering supply only through Installed Today, confirm the selected gas hot water system with your licensed gas fitter or installer. If choosing an eligible supplied-and-installed option, check exactly what is included before placing the order.

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