20L Instant Gas Hot Water Systems Australia
Our Top 3 20L Instant Gas Hot Water Systems
Choose How You Want to Order
Not every hot water job is the same. Choose supply only if you already have an installer arranged, or select a supplied and installed option where available.
Supply Only
Best if you already have a licensed plumber, gas fitter or electrician arranged.
Your product price is for the hot water system only. Installation is not included unless shown or selected separately.
Valves, old unit removal, disposal, electrical work, pipework changes, gas work and compliance upgrades may be required depending on your installation.
Supplied & Installed
Best if you want the hot water system and installation organised together.
Select your preferred system, answer the installation questions on the product page and choose any required installation options before checkout.
Installation availability and final requirements depend on your location, access, product type, existing services and site conditions.
Not Sure What You Need?
Hot water systems vary by size, energy source, household demand and installation setup.
Compare the available hot water systems below or use the selection tools throughout the site to narrow down the right option for your home.
Consider household size, energy source, available space, hot water demand, running costs and installation requirements before choosing.
20L Instant Gas Hot Water Systems for Brisbane, Gold Coast & Major Australian Metros
20L instant gas hot water systems, also known as 20L continuous-flow gas hot water systems, provide a practical middle-size option between compact 16L units and larger 26L systems.
They are commonly considered for small-to-medium homes, townhouses, units, rentals, couples, small families and one-to-two bathroom properties with moderate hot-water demand.
Installed Today supplies 20L continuous-flow systems across supported mainland Australian markets, with supplied and installed options available on selected systems in eligible Brisbane and Gold Coast service areas.
What Is a 20L Continuous Flow Gas Hot Water System?
How Does a 20L Instant Gas Hot Water System Work?
Continuous-flow gas systems do not keep a full tank of water hot. Instead, the burner operates when hot water is required and heats the water as it passes through the appliance.
The 20L description refers to the unit's nominal flow class under specified operating conditions.
Actual hot-water delivery depends on the incoming water temperature, required outlet temperature, gas supply, water pressure and the individual appliance.
Who Should Consider a 20L Instant Gas System?
Small Families
A 20L system provides more capacity than a compact 16L unit and can suit smaller families with moderate hot-water use.
Townhouses & Units
Compact wall-mounted continuous flow can suit properties where a large storage cylinder would use valuable space.
Rental Properties
20L can be a practical replacement class for smaller-to-medium rentals where expected household demand remains moderate.
One to Two Bathrooms
20L systems can suit one-to-two bathroom homes where several high-flow hot-water fixtures are not routinely operated together.
Existing 20L Replacement
If the old 20L appliance has always supplied enough hot water, another suitable 20L model is a logical replacement starting point.
Moderate Demand
20L is most appropriate where household expectations sit between compact low-demand and larger family-level continuous flow.
Where Does a 20L Instant Gas System Fit?
| Flow Class | Common Starting Point | Why Choose It | Main Question |
|---|---|---|---|
| 16L | Smaller homes and lower demand | Compact and practical where one main hot-water use dominates | Will 16L cover normal peak demand? |
| 20L | Small-to-medium households | Middle ground between compact and larger family systems | How often will hot outlets run together? |
| 26L | Larger family and stronger demand | More continuous-flow capacity for peak household use | Can the gas supply and plumbing support the larger unit? |
Should You Choose 20L Instead of 16L?
A 16L continuous-flow system can be suitable for smaller properties, granny flats, couples and lower-demand homes.
A 20L system provides additional flow capacity and can be a better fit where the household sits close to the limit of a 16L unit.
If an existing 16L system regularly struggles during peak periods, stepping up to 20L may be worth comparing, provided the gas supply, water conditions and installation support the larger appliance.
Should You Choose 20L or 26L Instant Gas?
A 20L unit is the practical middle option for moderate household demand.
A 26L system is more relevant where the home has a larger family, multiple bathrooms, heavier peak usage or stronger expectations around simultaneous hot-water use.
Bigger is not automatically better. A larger continuous-flow unit needs a gas supply and plumbing system capable of supporting its operating requirements.
The Number of Outlets Used Together Matters
Continuous-flow sizing should be based on peak simultaneous demand, not simply the number of people living in the property.
A household using one shower at a time can place much less demand on the unit than a property where two bathrooms regularly operate together.
When choosing 20L, consider:
- Number of showers
- Shower flow rates
- Kitchen use during showers
- Bath filling
- Morning peak usage
- Evening peak usage
- Incoming water temperature
- Desired outlet temperature
Why Incoming Water Temperature Affects Flow
A continuous-flow appliance needs to raise the incoming water to the required hot-water temperature.
When incoming water is colder, the appliance needs to add more heat for the same outlet temperature.
That is why the nominal 20L rating should not be treated as guaranteed usable hot-water flow in every climate and installation condition.
20L Natural Gas vs LPG Hot Water Systems
Natural Gas
Designed for properties connected to an appropriate mains Natural Gas supply.
LPG
Designed for properties using LPG and can suit homes without a mains Natural Gas connection.
Confirm Before Ordering
Natural Gas and LPG appliances are not interchangeable versions of the same unit. Confirm the gas type before purchase.
Gas Supply Is Critical to Instant Hot Water Performance
Continuous-flow hot-water systems can require substantial gas input when operating at higher hot-water demand.
Existing gas pipework needs enough capacity to supply the appliance together with other gas appliances that may operate at the same time.
If upgrading from 16L to 20L, changing from gas storage, or relocating the appliance, the existing gas supply should be checked rather than assumed suitable.
Rinnai and Rheem 20L Instant Gas Hot Water Systems
The current Installed Today 20L collection contains Rinnai Infinity B20 and Rheem 20L continuous-flow systems.
Both brands are currently represented in Natural Gas and LPG, giving four products across the live collection.
Compare gas type, dimensions, connection positions, controls, warranty, household suitability and installation requirements rather than choosing from brand alone.
Rinnai Infinity B20 Continuous Flow Hot Water
The Rinnai Infinity B20 sits within Rinnai's residential continuous-flow range and is currently available through Installed Today in both Natural Gas and LPG versions.
It provides a premium 20L option for homes wanting compact on-demand gas hot water within the middle residential flow class.
Confirm gas type, installation location, gas supply and household demand before choosing between the B20 and larger or smaller Infinity models.
Rheem 20L Continuous Flow Gas Hot Water
Rheem also offers 20L continuous-flow options in both Natural Gas and LPG through the current Installed Today range.
These provide another established residential 20L option for replacement jobs, townhouses, rental properties and moderate-use homes.
Compare the specific Rheem model against the existing appliance, connection positions, gas type, household demand and installation requirements.
Replacing a 20L Instant Gas Hot Water System
If the existing 20L unit has reliably supplied enough hot water, another suitable 20L system is normally the most logical sizing starting point.
A replacement still needs to match the property rather than just the nominal flow rate.
- Existing brand and model
- Natural Gas or LPG
- Existing flow class
- Current household demand
- Gas connection location
- Water connections
- Electrical requirements
- Clearances
- Wall mounting
- Drainage where required
Upgrading from 16L to 20L Instant Gas
Moving from 16L to 20L can provide additional flow capacity where the smaller system no longer comfortably handles household demand.
This can be useful after household occupancy increases or where multiple hot-water uses now overlap more often.
Before upgrading, check whether the existing gas line, regulator, water supply and installation position suit the new appliance.
When Does Downsizing from 26L to 20L Make Sense?
A 20L system can be worth considering if household occupancy and hot-water demand have reduced and the larger flow capacity of a 26L system is no longer required.
Downsizing should be based on expected simultaneous demand rather than product price alone.
If multiple bathrooms or high-flow fixtures remain in frequent use, retaining a larger system may be more appropriate.
Changing from Gas Storage to 20L Continuous Flow
Changing from a gas-storage cylinder to a 20L continuous-flow appliance can free up floor space and move the property to wall-mounted on-demand hot water.
It is not necessarily a simple product swap.
The conversion can involve gas-pipe sizing, wall mounting, plumbing changes, power supply, valves, drainage and current compliance requirements.
20L Instant Gas vs Gas Storage Hot Water
20L Instant Gas
Heats water on demand and uses a compact wall-mounted appliance rather than maintaining a stored tank of hot water.
Gas Storage
Stores heated water in a tank and can provide a simpler like-for-like pathway where a suitable gas-storage system is already installed.
Conversion
Choose based on total installation requirements and household use, not just the price of the replacement appliance.
Outdoor 20L Instant Gas Hot Water Systems
Standard residential 20L continuous-flow systems are commonly installed externally on an outside wall.
The selected position still needs to meet the appliance's requirements for clearances, ventilation, access, gas connection, water connections, electrical supply and other site conditions.
Do not assume an external model can be mounted inside an enclosed area. Indoor installations need an appliance and flue arrangement approved for that application.
Instant Gas Systems Can Still Need Electricity
Many residential continuous-flow gas systems use electricity for ignition, electronic controls and temperature management.
That means replacing or relocating a 20L appliance can involve electrical requirements even though gas is the primary heating energy source.
Check the specific product's electrical requirements and the existing supply before installation.
Temperature Controllers and 20L Continuous Flow
Selected continuous-flow systems support compatible temperature controllers or product-specific control options.
Controllers can provide convenient temperature management, but compatibility and available functionality vary between products.
Check the exact model and controller rather than assuming every 20L appliance supports the same accessories.
20L Instant Gas Hot Water Systems Brisbane
Brisbane is a primary 20L continuous-flow installation market for Installed Today. Selected systems can be ordered with professional installation in eligible Brisbane, Logan, Ipswich, Moreton Bay and Redlands service areas.
Common Brisbane applications include failed 20L replacements, townhouse and rental-property systems, upgrades from smaller 16L units and conversions from suitable gas-storage installations.
Final installation requirements depend on gas type, pipe sizing, water supply, appliance location, electrical requirements, access and current compliance conditions.
20L Instant Gas Hot Water Systems Gold Coast
Selected 20L continuous-flow gas hot water systems are also available supplied and installed across eligible Gold Coast service areas.
A 20L system can suit smaller families, townhouses, rental properties and moderate-demand homes where the gas supply and plumbing conditions are appropriate.
Confirm Natural Gas or LPG, simultaneous hot-water demand and installation requirements before ordering.
Buy 20L Instant Gas Hot Water Systems Across Major Australian Metros
Supply-only 20L systems are available for customers who already have appropriately licensed plumbing and gas trades arranged across supported mainland Australian markets.
Our main 20L instant gas markets include Brisbane, Gold Coast, Sunshine Coast, Sydney, Melbourne, Perth and Adelaide, together with Townsville, Cairns, Toowoomba, Newcastle, Central Coast, Wollongong and Geelong.
Brisbane and Gold Coast remain the primary Installed Today installation markets. Customers elsewhere can choose supply only where delivery is available and arrange their own appropriately licensed installer.
Choose How You Want to Order
Supply Only
Choose supply only if you already have an appropriately licensed plumber or gas fitter arranged and simply need the 20L appliance supplied.
Installation, valves, disposal, gas work, electrical work, pipe upgrades, wall mounting changes and compliance work are not included unless specifically shown.
Brisbane Installation
Selected 20L instant gas systems are available with installation in eligible Brisbane metro service areas.
Availability depends on product, postcode, gas type, existing installation and site conditions.
Gold Coast Installation
Selected 20L continuous-flow systems are also available supplied and installed in eligible Gold Coast areas.
Final requirements depend on the appliance and existing gas and plumbing setup.
Choose 20L When It Matches Peak Household Demand
A 20L instant gas system occupies a useful middle position in the residential continuous-flow range: more capacity than compact 16L systems without automatically moving to a larger 26L appliance.
Compare gas type, simultaneous fixture use, bathrooms, incoming water temperature, water pressure, gas-pipe capacity, dimensions, installation location and replacement compatibility before ordering.
If an existing 20L unit has performed well and household demand has not materially changed, another correctly selected 20L system is usually the most sensible sizing reference point.
20L Instant Gas Hot Water System FAQs
Common questions about choosing, ordering and installing 20L instant gas hot water systems for homes using natural gas or LPG.
What is a 20L instant gas hot water system best suited for?
A 20L instant gas hot water system is best suited to smaller and medium homes needing continuous flow gas hot water. It can be a practical option for homes with moderate hot water demand, one to two bathrooms, and either natural gas or LPG available.
How many people does a 20L instant gas hot water system suit?
A 20L instant gas hot water system commonly suits around 2 to 3 people, depending on shower flow rate, number of bathrooms, climate, gas supply, water pressure and household habits. Larger homes or heavy simultaneous hot water use may need to compare higher-flow continuous flow systems.
What does 20L mean on an instant gas hot water system?
20L refers to the hot water flow rate category of the unit. It gives an indication of how much hot water the system can deliver per minute under suitable conditions. Actual performance can depend on incoming water temperature, gas supply, water pressure and installation setup.
What is the difference between natural gas and LPG 20L models?
Natural gas and LPG models are made for different gas supplies. A natural gas unit is for homes connected to mains gas, while an LPG unit is for homes using bottled gas. The correct gas type must be selected before ordering because LPG and natural gas units are not interchangeable without the correct manufacturer-approved setup.
Is a 20L instant gas system better than a 16L system?
A 20L instant gas system can provide a higher flow rate than a 16L model under suitable conditions, making it a better option for some homes with higher hot water demand. The right size still depends on the number of outlets, shower habits, climate, gas supply and installation setup.
Can I buy a 20L instant gas hot water system supply only?
Yes. Choose supply only if you already have a licensed plumber or gas fitter arranged. Supply-only pricing is for the hot water system only and does not include installation, valves, old unit removal, disposal, gas work, electrical work, pipework changes, power point installation, controller wiring or compliance upgrades unless selected separately.
Can I order a 20L instant gas hot water system supplied and installed?
Yes. Supplied and installed options are available for selected 20L instant gas hot water systems in eligible Brisbane and Gold Coast service areas. Availability depends on your location, access, gas type, existing setup, gas compliance requirements, electrical requirements and site conditions.
Can I replace an old gas hot water system with a 20L instant gas unit?
In many cases, a 20L instant gas hot water system can replace an older gas unit, but the new system still needs to suit the existing location, gas supply, water pressure, pipe sizing, clearances, ventilation, electrical setup and current compliance requirements.
Are 20L instant gas hot water systems installed indoors?
Standard external 20L instant gas hot water systems are designed for outdoor installation. Do not assume a gas unit can be installed internally unless it is a manufacturer-approved internal or flued model and the installation meets all required ventilation, flueing and compliance requirements.
Where can a 20L instant gas hot water system be installed?
A 20L instant gas hot water system needs a suitable outdoor location with safe access, compliant plumbing, drainage, gas connection, clearances and ventilation. Most continuous flow systems also need a suitable nearby power point unless the selected model uses a different ignition setup.
Does installation include gas work?
Gas work is not automatically included unless shown in the selected installation option or chosen as an add-on. Some replacements may require gas compliance checks, regulator work, pipework changes, isolation valves, gas sizing upgrades or other work by a licensed gas fitter.
Does installation include electrical work or a power point?
Electrical work and power point installation are not automatically included unless shown in the selected installation option or chosen as an add-on. Some continuous flow gas systems require a nearby compliant power point, so this should be checked before ordering.
Does installation include old system removal and disposal?
Old system removal and disposal are not automatically included unless shown in the selected installation option or chosen as an add-on. Access, location, mounting, stairs, pipework and site conditions can affect what is required.
Is a 20L instant gas hot water system the same as gas storage?
No. A 20L instant gas hot water system is a continuous flow unit that heats water as it passes through the system. A gas storage hot water system heats and stores hot water inside a tank. The right choice depends on household demand, gas supply, space, installation setup and how the hot water is used.
Do you install 20L instant gas hot water systems in Brisbane and the Gold Coast?
Supplied and installed options are available in eligible Brisbane and Gold Coast service areas. Availability depends on the selected product, your address, gas type, access, existing system and installation requirements.