Instant Gas to Solar Hot Water
Instant Gas to Solar Hot Water: Is It Worth Switching?
From compact continuous-flow gas to stored solar hot water — what changes, where the tank goes and whether solar or heat pump makes more sense.
Replacing instant gas with solar hot water is more than a fuel change. A compact wall-mounted gas appliance becomes a storage system with a tank, roof-mounted solar collectors and backup heating. Gas pipework needs to be dealt with, a suitable tank position is required and household demand needs to be sized differently. If your main goal is reducing gas use rather than specifically wanting solar thermal, compare a heat pump as well — particularly where rooftop solar PV already exists.
Does Solar Suit Your Gas Replacement?
Start with your gas usage and roof. The biggest change is moving from tank-free continuous flow to stored hot water.
1 What does gas currently serve?
2 What is your roof like?
3 What matters most?
Guide only. Roof exposure, collector area, tank position, booster requirements, gas services, household demand and the selected replacement all need to be checked.
Can You Replace Instant Gas Hot Water With Solar Hot Water?
Yes. Instant or continuous-flow gas can be replaced with solar hot water where the property has suitable roof area and space for a storage tank. The biggest change is that the home moves from tank-free on-demand heating to stored hot water heated primarily by roof-mounted solar collectors and supported by a booster when required.
A Tank Is Added
Instant gas does not store hot water. Solar hot water does, so a suitable storage location becomes part of the conversion.
Collectors Go on the Roof
The solar system needs suitable collector area, exposure, access and roof conditions.
Gas Is Isolated
The gas connection serving the old continuous-flow unit needs to be safely dealt with as part of the conversion.
A Booster Is Required
Backup heating supports the solar system during periods when available solar contribution is not enough for household demand.
The Biggest Change: Continuous Flow Becomes Stored Hot Water
Instant gas and solar hot water deliver hot water in fundamentally different ways. A continuous-flow gas unit heats water as it passes through the appliance. Solar stores heated water ready for later use.
Instant / Continuous-Flow Gas
Water passes through a compact wall-mounted appliance and is heated by the gas burner when a hot tap is opened.
There is no large reserve tank, so household sizing is commonly discussed using appliance flow capability and simultaneous outlet demand.
Stored Solar Hot Water
Solar collectors capture heat and transfer it into a stored volume of water. The household then draws from that stored reserve.
Tank capacity, collector area, household demand and booster recovery all become important parts of sizing.
Split Solar or Close-Coupled Solar After Instant Gas?
Because an instant-gas property does not already have a storage tank, the new tank location is one of the most important decisions in the conversion.
Ground-Level Tank + Roof Collectors
Split solar places the storage cylinder at ground level and the thermal collectors on the roof.
This keeps the tank accessible for servicing and can suit properties with a practical external ground-level area near existing hot and cold services.
Solar pipework connects the collector array to the storage system.
Tank + Collectors on the Roof
Close-coupled solar places both the storage cylinder and solar collectors on the roof.
That can preserve ground space and may appeal to customers moving away from compact instant gas who do not want a large cylinder beside the house.
Roof loading, pitch, access and structural suitability become particularly important.
Why Change From Instant Gas to Solar Hot Water?
The strongest reason is normally to move a major household energy load away from ongoing gas consumption and toward renewable solar energy.
Reduce Gas Consumption
Solar thermal energy can provide a substantial portion of the heat required for household hot water without operating a gas burner every time water is used.
Directly Use Sunshine
Dedicated roof collectors convert sunlight directly into useful heat for the stored water.
Move Toward Electrification
Where hot water is the property's last gas appliance, replacing it can create an opportunity to consider whether the household still needs an ongoing gas connection.
Instant Gas, Solar & Heat Pump: Current JR Starting Prices
Instant gas starts from a very different installation base because it does not require a large storage cylinder or solar collector array. Compare the complete installed conversion rather than the product price alone.
The simplest pathway where the existing gas position, pipework and hot-water layout remain suitable.
Current JR advertised starting price. Final price depends on unit size, gas type and installation conditions.
Adds renewable solar-thermal collection, storage and backup heating for suitable properties.
Eligible systems may qualify for JR's current upfront STC pathway.
Also removes gas from water heating while avoiding dedicated solar-thermal collectors and using efficient electric heat transfer.
Eligible heat pumps may also qualify for JR's current upfront STC pathway.
Instant Gas vs Solar Hot Water vs Heat Pump
| Consideration | Instant Gas | Solar Hot Water | Heat Pump |
|---|---|---|---|
| Hot-water delivery | Continuous flow | Stored hot water | Stored hot water |
| Storage tank | No | Yes | Yes |
| Main heating source | Natural gas or LPG | Solar thermal + booster | Ambient-air heat + electricity |
| Roof equipment | None for water heating | Dedicated solar collectors | No dedicated solar-thermal collectors |
| Solar PV compatibility | PV does not power the gas burner | Separate solar-thermal system | Can directly use household PV electricity |
| Gas use | Gas used while water is heated | Can remove gas from hot-water heating depending on booster configuration | No gas required for normal hot-water heating |
| Operating noise | Burner / fan operation varies by model | No heat-pump compressor; split systems may use circulation equipment | Compressor and fan operate 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 hot water | Direct solar thermal heating | Efficient gas-free hot water with simple PV integration |
Where Does the Solar Tank Go When You Currently Have Instant Gas?
This is often the first physical question to answer. An instant gas system may occupy only a small section of wall, while solar hot water needs substantial storage capacity somewhere on the property.
Ground-Level Position
Split solar needs enough space for a storage cylinder, suitable base, service access, plumbing connections and drainage.
Roof-Mounted Position
Close-coupled solar can place the tank on the roof but increases the importance of structure, weight, access and installation conditions.
Plumbing May Need Extension
The best storage location may be several metres from the old wall-mounted gas unit, so hot and cold services can require redirection.
Is Your Roof Suitable for Solar Hot Water?
This requirement did not matter to your instant-gas system. It becomes central once dedicated solar collectors are introduced.
Usable Collector Area
Enough practical roof area is needed for the selected collector configuration.
Solar Exposure
Collector positioning and available sunlight influence how much useful heat the system can capture.
Shading
Trees, neighbouring buildings and roof structures can reduce useful solar exposure.
Access
Roof height, pitch, material and safe access affect installation complexity and future servicing.
Structural Suitability
Close-coupled solar places the weight of the storage tank and water on the roof as well as the collector assembly.
Existing Solar PV
Existing PV can occupy the roof area solar thermal would otherwise use and can also strengthen the case for a heat-pump alternative.
What Happens to the Existing Gas Connection?
The gas service feeding the old continuous-flow water heater needs to be safely isolated and dealt with as part of the replacement. What happens to the property's broader gas supply depends on whether other gas appliances remain.
Gas Supply Can Stay
Removing the hot-water appliance does not require the customer to remove gas from the entire property if cooktops, fireplaces or other appliances still need the supply.
The redundant hot-water branch still needs to be safely dealt with.
You Can Consider Full Gas Disconnection
If no other gas appliances remain, replacing gas hot water can create an opportunity to consider ending the property's ongoing gas service.
That is a separate retailer or distributor pathway and does not happen automatically simply because the hot-water appliance has been removed.
Solar Still Needs a Backup Heating Strategy
Solar thermal contribution varies with weather, season, household demand and system sizing. A suitable booster supports the stored hot water when solar energy alone is not enough.
Electric Booster
An electrically boosted system keeps the replacement hot-water pathway independent of the old gas burner and can support broader household electrification.
Poor Solar Conditions
Cloud, rain and periods of lower solar availability can increase the amount of backup heating required.
Household Demand Matters
Heavy use can consume stored solar-heated water faster than the collector system can replenish it, making tank sizing and booster recovery important.
Already Have Solar PV? Heat Pump Becomes a Very Important Comparison
Solar hot water and solar PV use the sun differently. Solar hot water needs dedicated thermal collectors, while a heat pump can use electricity from the PV panels you may already have.
Instant Gas
Rooftop PV cannot provide the natural gas or LPG consumed by the burner.
Solar Thermal
Dedicated collectors occupy their own roof area and directly capture thermal energy for water heating.
Heat Pump + PV
A heat pump can operate during daylight hours and use household-generated electricity without requiring a separate thermal collector array.
Where the home already has substantial rooftop PV, moving from instant gas to heat pump can be a very natural electrification pathway: gas is removed from water heating, existing PV can contribute to operation and valuable roof space does not need to be allocated to another solar technology.
Solar or Heat Pump: Which Makes More Sense After Instant Gas?
Both replace gas-fired continuous flow with stored renewable or high-efficiency hot water. The better pathway depends on the roof, tank location, solar setup and what the customer is actually trying to achieve.
You Have an Excellent Roof and Specifically Want Solar Thermal
Strong unshaded collector exposure, practical roof access and a preference for direct solar heating make the solar conversion genuinely compelling.
Solar can also suit customers who want efficient hot water without a heat-pump compressor and fan.
You Mainly Want to Leave Gas Efficiently
Heat pump avoids dedicated thermal collectors, works independently of solar-roof exposure and can directly use electricity from an existing PV system.
It is particularly worth comparing where the roof is shaded, crowded with PV or difficult to access.
Can an Instant-Gas-to-Solar Upgrade Qualify for STCs?
Eligible listed solar water heaters can create Small-scale Technology Certificates when the exact system and completed installation satisfy the current scheme requirements. Eligible listed air-source heat pumps can also qualify.
Eligible Systems Can Qualify
The exact solar system, approved configuration, installation date and location all form part of the eligibility pathway.
Eligible Heat Pumps Can Qualify Too
If the customer is primarily trying to leave gas, heat pump should not be ignored simply because the word solar sounds more renewable. Eligible heat pumps also participate in the STC scheme.
When Instant Gas to Solar Can Genuinely Make Sense
Solar deserves to win where the property and customer priorities genuinely suit what it does differently.
Excellent Sunny Roof
Good collector exposure gives solar thermal the opportunity to provide a substantial share of household water heating.
Direct Solar Thermal Is Preferred
The customer specifically wants water heated from dedicated solar collectors rather than through a gas burner or refrigeration cycle.
Compressor Noise Is Unwanted
Solar avoids the compressor and large outdoor fan associated with heat-pump operation.
Hot Water Is the Last Gas Appliance
Replacing instant gas creates an opportunity to remove a major gas load and potentially consider broader household electrification.
Ground Space Can Be Preserved
A suitable close-coupled solar system can put the storage cylinder on the roof rather than occupying ground space beside the home.
Long-Term Energy Reduction Matters
Strong solar contribution can substantially reduce purchased energy compared with continuously burning gas whenever hot water is required.
When Heat Pump Is Usually the Stronger Move Away From Instant Gas
If the objective is mainly to stop using gas for hot water rather than specifically to install solar thermal, heat pump often deserves the first comparison.
Rooftop Solar PV Already Exists
Heat pump can use electricity produced by the existing PV system instead of requiring a second dedicated solar collector technology.
Roof Is Shaded
A heat pump does not depend on dedicated sunny collector roof area to deliver efficient hot water.
Roof Space Is Limited
Keeping hot-water collection at ground level can preserve valuable roof area for existing or future PV panels.
Roof Access Is Difficult
Heat pump can avoid the collector mounting and dedicated solar pipework required by solar thermal.
Lower Upfront Conversion Cost Matters
Both pathways require moving from tank-free gas to stored hot water, but heat pump can avoid the additional solar-collector installation component.
Simple Electrification Is the Goal
Heat pump provides a direct all-electric replacement pathway without retaining gas for water heating or introducing dedicated solar-thermal hardware.
When Staying With Instant Gas Can Still Make Sense
Moving away from instant gas introduces storage and substantial installation changes. There are situations where remaining with continuous flow is still practical.
Tank Space Is Extremely Limited
Instant gas remains one of the most compact whole-home hot-water options where there is no practical storage-cylinder location.
Continuous Flow Is the Priority
If the household strongly values tank-free on-demand delivery, a storage-based solar or heat-pump system changes that experience.
Existing Gas Setup Is Straightforward
Where the existing gas unit can be replaced in essentially the same position without significant service changes, it may provide the lowest-complexity replacement.
How an Instant-Gas-to-Solar Conversion Works
Compare Solar & Heat Pump
Decide whether direct solar thermal or efficient electric hot water better suits the property before committing to the conversion.
Assess the Roof
Confirm collector area, sunlight, shading, roof type, structural requirements and safe installation access.
Choose the Tank Layout
Decide between a ground-level split-solar tank and a suitable close-coupled roof-mounted system.
Size Tank & Collectors
Match stored capacity and collector configuration to occupancy, bathrooms and normal household hot-water use.
Disconnect the Instant Gas Unit
Remove the old continuous-flow appliance and safely deal with its gas and water connections.
Install & Commission Solar
Install the tank, collectors, pipework, booster, valves and controls, then test and commission the completed system.
Instant Gas to Solar Hot Water FAQs
Can I replace instant gas hot water with solar hot water?
Yes. Continuous-flow gas can be replaced with solar hot water where the property has suitable collector roof area and somewhere appropriate for the new storage tank.
Is changing from instant gas to solar worth it?
It can make sense where the home has excellent solar exposure and the customer wants direct solar thermal heating, lower reliance on gas or quiet renewable hot water. Heat pump should also be compared where the main objective is simply to move away from gas efficiently.
Does solar hot water need a tank?
Yes. Domestic solar hot-water systems store heated water in a cylinder. The tank may be at ground level in a split system or mounted on the roof as part of a suitable close-coupled system.
Where will the tank go if I currently have instant gas?
Split solar needs a suitable ground-level tank position with plumbing, drainage and service access. Close-coupled solar can place the storage tank on the roof where the structure and installation conditions are suitable.
Can a 26L instant gas system be replaced with a 270L or 300L solar system?
The figures are not directly equivalent. Instant gas litres-per-minute describes flow capability, while solar tank litres describe stored capacity. Solar sizing should consider household occupancy, bathrooms, peak demand, usable storage and booster recovery.
Will solar hot water still give us endless hot water?
Solar hot water is a storage system, so it does not reproduce continuous-flow delivery in exactly the same way as instant gas. Available hot water depends on stored capacity, temperature, household use, solar contribution and booster recovery.
What happens to the old gas connection?
The gas connection serving the old water heater needs to be safely isolated or altered as required. The property's overall gas supply can remain if other appliances still use it.
Can I disconnect gas completely after changing to solar hot water?
Potentially, if hot water is the last gas appliance at the property. Removing the appliance does not automatically close the gas account or disconnect the broader gas service, so that needs to be considered separately with the relevant provider.
What happens on cloudy or rainy days?
Solar contribution can reduce during poor weather or periods of lower solar availability. The system's booster supports the stored hot water when solar energy alone does not meet household demand.
Does solar hot water use electricity?
Many solar systems use an electric booster, and some split systems also use electrical controls or circulation equipment. The exact requirements depend on the selected system.
What if I already have rooftop solar PV?
Existing PV makes heat pump particularly worth comparing. A heat pump can use electricity generated by the PV system already on the roof, while solar hot water requires its own dedicated thermal collector area.
Is heat pump or solar better after instant gas?
Solar can be especially attractive where the roof has excellent exposure and the customer specifically wants direct solar thermal heating or quiet operation. Heat pump can be stronger where rooftop PV already exists, roof space is limited, solar exposure is poor or the main goal is simply efficient electrification.
Does solar hot water qualify for STCs when replacing gas?
Eligible listed solar water heaters can qualify for Small-scale Technology Certificates when the exact system and completed installation satisfy current scheme requirements.
Does heat pump qualify for STCs when replacing instant gas?
Eligible listed air-source heat pumps can also qualify for Small-scale Technology Certificates when the exact model and completed installation satisfy current scheme requirements.
Does JR's $1,000 upfront STC discount apply to solar?
JR's current policy applies its $1,000 including GST upfront STC discount to eligible solar-hot-water and heat-pump systems supplied and installed by JR, subject to final STC eligibility and assignment requirements.
Moving Away From Instant Gas? Compare Both Renewable Pathways
Solar hot water can be an excellent choice where the roof has strong exposure and you specifically want direct solar thermal heating. If the main goal is simply to stop burning gas for hot water, compare a heat pump too — particularly if you already have rooftop solar PV, limited collector roof area or want a simpler ground-level renewable upgrade.