Instant Gas to Solar Hot Water: Is It Worth Upgrading?
Instant Gas to Solar Hot Water: Is It Worth Switching?
Solar can be an excellent move away from continuous-flow gas when the roof is genuinely strong - but it also introduces a storage tank, roof collectors and a booster, so the property needs to suit the change.
Instant gas heats water only as it is used and normally occupies very little ground space. Solar hot water changes the home to stored hot water, adds dedicated solar collectors or evacuated tubes and uses a booster when solar contribution is not enough. That can reduce gas use substantially, but the conversion is more involved than replacing one storage system with another.
Does Solar Suit Your Instant-Gas Replacement?
This is a preliminary guide. Final suitability depends on roof exposure, tank space, collector layout, structure and access, gas services, booster requirements, electrical supply and household demand.
1What is the roof like?
2Is there room for a storage tank?
3What matters most?
Guide only. Solar collector orientation, shading, roof condition, structural requirements, tank location, gas isolation, booster type, drainage and household demand must be checked before finalising a conversion.
Can You Replace Instant Gas With Solar Hot Water?
Yes. Natural-gas or LPG continuous-flow hot water can be replaced with solar hot water where the property has suitable roof exposure and somewhere to store hot water. The biggest physical change is that instant gas has no storage cylinder, while every solar-hot-water system needs one.
Instant Gas vs Solar vs Heat Pump: What Actually Changes?
All three can deliver reliable household hot water, but the infrastructure and energy source are very different.
| Consideration | Instant Gas | Solar Hot Water | Heat Pump |
|---|---|---|---|
| Heating method | Gas burner heats water on demand | Direct solar thermal + booster | Heat transferred from surrounding air + electricity |
| Storage tank | No | Yes | Yes |
| Ground space | Very low | Needed for split solar; close-coupled can move tank to roof | Normally needs a ground-level tank position |
| Roof equipment | None for hot water | Dedicated collectors | No thermal collectors required |
| Solar PV compatibility | PV does not power the gas burner | Uses separate thermal collectors | Strong advantage Can use household PV electricity |
| Operating noise | Burner / fan depending on appliance | Usually quiet; split systems may use circulation equipment | Compressor and fan while heating |
| STCs | No renewable-hot-water STC pathway | Eligible listed systems may qualify | Eligible listed systems may qualify |
| Strongest reason to choose | Compact continuous flow where gas already exists | Excellent sunny roof + direct solar heating | Efficient gas-free storage, especially with PV |
Why Move From Instant Gas to Solar Hot Water?
The main attraction is replacing ongoing gas combustion for water heating with direct solar thermal energy, while retaining a booster for periods when solar contribution is not enough.
Reduce Gas Consumption
Solar collectors can provide a large share of the energy used to heat the stored water when solar conditions are favourable.
Use Direct Solar Heat
Solar thermal captures sunlight specifically for water heating rather than converting it to electricity first.
Potential STCs
Eligible listed solar water-heater systems can create Small-scale Technology Certificates when installed in the approved configuration.
Move Away From Gas
If hot water is the last gas appliance, the conversion can create an opportunity to separately consider whether the broader gas service is still required.
Quiet Renewable Option
Solar avoids the compressor and large outdoor fan used by a heat pump, which can matter in noise-sensitive properties.
Stored Reserve
The conversion changes the home from continuous flow to a stored reserve, which some households prefer for predictable hot-water availability.
Already Have Solar PV? Heat Pump Becomes a Very Strong Comparison
Solar thermal and solar PV are different technologies. If the roof already carries useful PV capacity, a heat pump can use that generated electricity efficiently without adding a second solar platform dedicated to hot water.
Instant Gas
Rooftop PV cannot provide the natural gas or LPG burned by the current appliance.
Solar Thermal
Dedicated collectors directly heat the water but need their own roof area, solar pipework and system-specific servicing.
Heat Pump + PV
A heat pump can operate during solar-production hours and use household-generated electricity while removing gas from normal hot-water heating.
If strong rooftop PV is already installed and a ground-level tank position is workable, we would normally compare heat pump before adding solar thermal. It can use the solar platform the home already owns and avoids dedicated collector space.
The Biggest Change: Instant Gas Has No Tank, Solar Does
An instant-gas appliance is normally wall mounted and compact. Solar hot water needs a storage cylinder, so the first practical question is where that stored water will live.
Split Solar
A ground-level tank connects to collectors on the roof. This is often the easier solar configuration where there is suitable outdoor tank space and accessible pipe routes.
Close-Coupled Solar
The tank and collectors are mounted on the roof, preserving ground space but increasing roof-loading, access and structural considerations.
New Base & Drainage
A ground-level cylinder may need a suitable base, pressure/temperature relief drainage and service clearances that the old instant-gas site never required.
New Pipe Routes
The installer may need to connect existing hot and cold services to a new tank position and run solar circulation pipework to the roof.
Booster Connection
Electric or gas boosting needs the appropriate supply, isolation, controls and compliance work for the chosen solar system.
Heat Pump Alternative
The same new ground-level tank space may suit a heat pump, without needing thermal collectors or solar circulation pipework.
When Solar Hot Water Is the Stronger Upgrade
Solar deserves the strongest recommendation when the property itself gives direct solar thermal a real advantage.
Excellent Sunny Roof
Strong unshaded exposure gives the collector array its best opportunity to carry a large share of the water-heating load.
You Specifically Want Direct Solar Thermal
If the goal is to heat water directly from the sun rather than use gas or a refrigeration cycle, solar is the obvious pathway.
Quiet Operation Matters
Solar avoids a heat-pump compressor and large fan, which can be valuable near bedrooms or close boundaries.
Roof Access Is Straightforward
Simple safe access helps both initial collector installation and long-term servicing.
Close-Coupled Solar Solves the Space Problem
If ground space is tight but the roof structure suits the load, roof-mounted storage can preserve the compact footprint that made instant gas attractive.
Gas Is Being Phased Out
Solar with an electric booster can remove gas from normal water heating and may support a wider household electrification plan.
When We Would Recommend Heat Pump Instead
If solar is only marginally better, we would usually favour heat pump because it achieves efficient gas-free stored hot water without relying on dedicated collector roof space.
Rooftop PV Already Exists
A heat pump can use electricity from the solar system already installed rather than competing for roof area with another collector technology.
Roof Is Shaded or Crowded
Heat-pump efficiency does not depend on dedicated sunny collector exposure in the way solar thermal does.
Roof Access Is Difficult
Ground-level heat-pump servicing avoids collector work on a steep, high or awkward roof.
A Good Tank Site Exists
If there is already a sensible outdoor space for a new cylinder, heat pump becomes a very clean gas-to-electric conversion.
You Want Simpler Future Servicing
The main working components can usually be accessed from ground level rather than split between a tank and roof array.
The Choice Is Close
Where solar has no clear roof or noise advantage, heat pump is usually our preferred long-term pathway.
What Happens to the Existing Gas Connection?
The gas branch serving the old continuous-flow appliance needs to be safely isolated or altered. Whether the property keeps its broader natural-gas or LPG supply depends on what else still uses gas.
Keep the Property Gas Supply
Cooktops, fireplaces or other gas appliances can continue using the gas service. Only the redundant hot-water branch needs to be dealt with as part of the conversion.
Consider Full Gas Disconnection Separately
Removing the instant-gas heater may create an opportunity to review whether the property still needs an ongoing gas account or LPG supply. That wider disconnection is separate from simply removing the hot-water appliance.
What Happens When the Sun Is Not Providing Enough Heat?
Solar hot water still needs backup for poor weather, winter conditions, unusually high demand or periods when collectors cannot provide enough useful heat.
Electric Boosting
An electric element can bring stored water to temperature when solar contribution is insufficient and allows hot water to move completely away from gas.
Gas Boosting
Some solar arrangements use gas boosting. This can retain strong backup performance but also preserves gas infrastructure and fuel dependency.
Sizing Matters
Collector area, tank capacity, household demand and local solar conditions affect how often boosting is required.
Can Instant-Gas-to-Solar Replacement Qualify for STCs?
Potentially, yes. The federal Small-scale Renewable Energy Scheme includes eligible solar water heaters and eligible air-source heat pumps. The new system must be a listed model and installed in its approved configuration within the eligibility period.
Eligible Systems Can Receive STCs
The exact collector, tank and approved configuration must match the current Clean Energy Regulator listing and scheme rules.
The Alternative Can Qualify Too
Eligible air-source heat pumps can also create STCs, so the presence of an incentive does not by itself make solar the better technology.
Confirm the Claim Pathway Before Installation
Product eligibility alone does not complete an STC or state incentive claim. Confirm the installer, registered agent and any pre-approval requirements first.
Current Instant Gas Starting Price vs a Solar Conversion
Instant gas is compact and can be cheaper to replace like-for-like where the gas supply remains suitable. Solar adds a tank, roof collectors, mounting and booster work in exchange for using renewable solar energy for much of the water-heating load.
Usually the simplest pathway where the existing gas supply, wall position, water services and power point remain suitable.
Current Installed Today instant-gas collection starting price. Final installed cost depends on gas type, flow rate and installation scope.
Best where roof exposure is excellent, a tank position is practical and the homeowner genuinely wants direct solar thermal.
Allow for a storage tank, collectors, mounting, roof access, solar pipework, booster requirements and gas isolation or alteration.
How an Instant-Gas-to-Solar Conversion Usually Works
The exact scope depends on whether split or close-coupled solar is chosen and whether the old gas service remains for anything else.
Assess Roof & Tank Space
Check solar exposure, shading, roof structure and access, plus a suitable storage location if split solar is being considered.
Choose the Solar Configuration
Compare split solar with a ground tank against close-coupled solar with the tank and collectors on the roof.
Confirm Booster & Gas Changes
Decide between electric or gas boosting and confirm how the redundant instant-gas connection will be isolated or altered.
Install & Commission
Remove the old appliance, install the tank and collectors, connect the booster and services, and complete the eligible certificate pathway where applicable.
Supply Only vs Supplied & Installed
Installed Today sells hot-water products online with supply-only ordering across supported Australian metro areas and supplied-and-installed options where available in eligible Brisbane and Gold Coast service areas. A solar conversion can involve roof work and system-specific installation requirements beyond a standard instant-gas replacement.
Confirm the Full Solar Layout First
Arrange appropriately licensed trades to confirm collector position, tank layout, booster, plumbing, gas changes, roof work and incentive pathway before purchasing the system.
Availability Depends on Product & Location
Where an Installed Today installation option is offered, review the product's installation inclusions and any additional roof, tank-position, electrical, gas or plumbing work required for the property.
Instant Gas to Solar Hot Water FAQs
Can I replace instant gas with solar hot water?
Yes. Instant gas can be replaced with split or close-coupled solar hot water where the roof, storage location, services, booster and installation conditions suit the selected system.
What is the biggest change when moving from instant gas to solar?
You need to introduce a storage tank. Instant gas normally has no stored reserve, while solar hot water always stores heated water either in a ground-level cylinder or a roof-mounted tank.
Is solar hot water cheaper to run than instant gas?
A well-sited solar system can substantially reduce purchased energy for water heating by using direct solar thermal energy. Actual cost depends on solar contribution, booster use, gas and electricity tariffs, household demand and system design.
Should I choose solar or a heat pump after instant gas?
Solar is strongest where the roof is excellent and direct solar thermal or quieter operation is specifically wanted. Heat pump is usually stronger where rooftop PV already exists, roof space is limited, the roof is shaded or easier ground-level servicing is preferred.
What happens to the old gas connection?
The branch serving the old instant-gas appliance must be safely isolated or altered. The broader gas supply can remain if other appliances still use it.
Can solar hot water remove gas completely?
Potentially, if the solar system uses an electric booster and no other gas appliances remain. Removing the hot-water appliance does not automatically disconnect the property gas account or network service.
Does solar hot water still need a booster?
Yes. Solar hot water needs backup heating for low solar contribution, poor weather or high household demand. Depending on the system, this may be electric or gas boosting.
Can instant-gas-to-solar replacement qualify for STCs?
Eligible listed solar water-heater systems can create STCs when installed in the approved configuration within the model's eligibility period and all scheme requirements are met.
What if I already have rooftop solar PV?
Existing PV strengthens the heat-pump comparison because a heat pump can use household-generated electricity without adding a separate solar-thermal collector array. Solar thermal can still make sense if roof area remains excellent and direct solar heating is specifically preferred.
Can close-coupled solar keep my ground space free?
Potentially. Close-coupled solar places the storage tank and collectors on the roof, but the roof structure, loading, pitch, access and selected system all need to suit that arrangement.
When would staying with instant gas still make sense?
Instant gas can remain practical where ground space is extremely limited, the existing gas service is staying for other appliances, continuous-flow delivery is a priority or the roof is unsuitable for solar and a heat-pump location is also poor.
Replacing Instant Gas? Check the Roof and Tank Space Before Choosing Solar
Instant-gas-to-solar can be an excellent move where the roof is genuinely strong, a storage solution works and direct solar thermal is the goal. If rooftop PV already exists or solar conditions are only marginal, compare a heat pump before committing - it may deliver the stronger overall pathway with less roof-specific infrastructure.
