Instant Gas to Heat Pump Hot Water
Instant Gas to Heat Pump Hot Water: Is It Worth Upgrading?
From continuous-flow gas to stored heat-pump hot water — what changes, where the tank goes and what the conversion involves.
Replacing instant gas hot water with a heat pump is a bigger physical change than replacing one storage tank with another. Instant gas is compact and heats water as you use it; a heat pump stores hot water in a tank. The conversion therefore needs to consider tank space, recovery, electrical supply, gas isolation, drainage, solar use and household demand.
Does Heat Pump Suit My Home?
The biggest difference from instant gas is that a heat pump needs somewhere to store hot water. Start with the space available.
1 Do you have room outside for a storage tank?
2 What gas supply does the current unit use?
3 What matters most?
Guide only. Tank space, hot-water demand, recovery, electrical requirements, gas isolation, airflow, drainage and noise need to be checked for the selected system.
Can You Replace Instant Gas Hot Water With a Heat Pump?
Yes. An instant gas or continuous-flow gas water heater can be replaced with a heat pump. The major difference is that the existing gas unit is usually a compact wall-mounted appliance with no hot-water storage tank, while a heat pump normally needs a full-size storage cylinder and suitable ground-level installation area.
Tank Space
A heat pump needs space for stored hot water. Finding the correct tank position is often the first major question in an instant-gas conversion.
Gas Connection
The gas connection serving the old continuous-flow unit needs to be safely isolated and appropriately dealt with.
Electrical Supply
The new heat pump uses electricity, so the electrical requirements of the selected system need to be provided at the new installation position.
Stored-Hot-Water Sizing
Continuous-flow capacity is usually discussed in litres per minute. Heat pumps instead need to be sized around stored volume, usable hot water and recovery.
The Biggest Change: Continuous Flow Becomes Stored Hot Water
This is the key difference to understand before changing technologies. Instant gas heats water as it flows through the appliance. A heat pump heats and stores a tank of water for the household to use later.
Hot Water on Demand
A correctly sized continuous-flow gas system can keep heating while hot water is being drawn, rather than relying on a preheated tank.
Its compact wall-mounted footprint is also one of the biggest advantages for properties with limited ground space.
Stored Water + Recovery
A heat pump stores hot water in a tank. The household therefore needs enough usable storage and recovery performance to cover normal demand.
Correct sizing becomes particularly important for larger households, multiple bathrooms and periods of concentrated hot-water use.
Why Change From Instant Gas to Heat Pump Hot Water?
Instant gas has genuine strengths, particularly compact size and continuous-flow delivery. The main reasons to move away from it are usually different: reducing gas use, making use of rooftop solar, changing the home's energy mix or choosing an eligible renewable hot-water technology.
Reduce Gas Dependence
A heat pump removes gas from water heating. If hot water is the home's final gas appliance, the conversion may also support a broader move away from an active gas supply.
Use Rooftop Solar
A heat pump uses electricity, so suitably controlled daytime operation can allow rooftop solar generation to contribute directly to water heating.
Eligible STCs
Eligible listed air-source heat pumps can create Small-scale Technology Certificates when the exact model and completed installation satisfy current scheme requirements.
Instant Gas vs Heat Pump: Current JR Starting Prices
Replacing instant gas with another instant gas unit and converting to a heat pump are fundamentally different jobs. Compare the complete installed scope rather than product price alone.
Usually the more direct replacement pathway where the existing gas service, location and pipework remain suitable.
Current JR advertised starting price. Final price depends on unit size, gas type and installation scope.
Changes the home from continuous-flow gas to electrically powered stored hot water with heat-pump recovery.
Current JR advertised starting price. STC eligibility depends on the exact system and completed installation.
Instant Gas vs Heat Pump Hot Water
| Consideration | Instant Gas | Heat Pump |
|---|---|---|
| Hot-water delivery | Heats water as it is used | Stores heated water in a tank |
| Physical footprint | Compact wall-mounted appliance | Requires storage-cylinder space |
| Energy source | Natural gas or LPG | Electricity |
| Rooftop solar | Solar PV cannot directly power the gas burner | Can often operate during solar-production hours |
| STC eligibility | Not eligible simply because the gas unit is new | Eligible listed systems may qualify |
| Long shower / high-use periods | Continuous operation when correctly sized and supplied | Depends on stored volume and recovery |
| Electrical requirement | Varies by gas appliance | Electrical supply required for heat-pump operation |
| Typical reason to choose | Compact size and continuous-flow delivery | Electrification, solar use and efficiency |
Where Does the Heat Pump Go if the Instant Gas Unit Is on the Wall?
This is often the most important site question. A compact continuous-flow heater may occupy very little wall space, while the replacement heat pump needs a suitable position for a substantial storage cylinder.
Ground-Level Space
The proposed position needs enough physical room for the selected tank and any required clearances.
Stable Base
The filled cylinder is much heavier than a wall-mounted instant gas unit, so suitable stable support is required.
Plumbing Route
The hot and cold water services may need to be extended or redirected from the old instant-gas position to the new tank.
Airflow
The heat pump requires the airflow and clearances specified for the selected model.
Drainage
A suitable pathway is required for storage-system discharge and heat-pump condensate.
Noise & Access
Bedrooms, neighbours, windows and future service access should all be considered before the position is finalised.
What Changes During an Instant-Gas-to-Heat-Pump Conversion?
Instant Gas Unit Removed
The existing continuous-flow heater is isolated, disconnected and removed from service.
Gas Is Dealt With
The gas connection serving the old appliance is appropriately isolated or altered for the finished installation.
Tank Position Created
The heat pump needs an appropriate installation position with stable support, airflow and service access.
Plumbing Is Redirected
Hot and cold water pipework is adapted to the new storage-system location and valve arrangement.
Electricity Is Provided
The required electrical connection and protection are provided for the selected heat pump.
System Is Commissioned
The tank is filled and the heat pump is tested, configured and checked before normal use.
What Electrical Work Is Needed?
The new appliance is electrically powered, so the available electrical infrastructure needs to be checked against the exact heat pump selected. This is particularly important because the old instant gas unit may not have anything comparable to the electrical supply required by the new system.
New Installation Position
Suitable power needs to reach the position chosen for the heat-pump tank, which may be different from the old wall-mounted gas unit.
Model Requirements
Connection and protection requirements vary between heat pumps, so the exact product should be selected before the final electrical scope is determined.
Existing Switchboard
Existing electrical infrastructure needs to support the selected appliance and required installation arrangement.
What Happens to the Gas Connection?
Removing instant gas from the hot-water system does not necessarily mean the entire property stops using gas. The answer depends on whether gas cooking, heating or other gas appliances remain.
Keep the Main Gas Service
If the home still uses gas for cooking, room heating, fireplaces or another appliance, the property gas service can remain while the old hot-water connection is dealt with separately.
Consider Whether Gas Is Still Needed
If instant hot water is the property's only remaining gas appliance, changing to heat pump creates an opportunity to consider whether maintaining the broader gas connection still makes sense.
Have Rooftop Solar? Heat Pump Can Use What Instant Gas Cannot
Instant gas uses gas energy when hot water is required. A heat pump uses electricity, creating an opportunity to schedule water heating around household solar production where the selected system and normal hot-water demand allow it.
Heat During Solar Hours
Daytime operation can move more of the water-heating load into periods when the solar system is generating electricity.
Store Heat for Later
The storage cylinder keeps the heated water available for later household use after peak solar generation has passed.
Correct Sizing Still Matters
Solar timing does not replace the need for enough storage and recovery to cover the household's actual hot-water demand.
Can You Get STCs When Replacing Instant Gas With a Heat Pump?
Potentially. The old water heater being instant gas does not itself prevent a new eligible heat pump from qualifying. The exact air-source heat-pump model, listed configuration and completed installation determine the STC pathway.
Choose an Eligible Model
The exact heat pump needs to appear on the applicable current eligibility register.
Install the Listed Configuration
The completed system needs to match its eligible configuration and installation requirements.
Complete the Claim Pathway
The installation and required evidence support the final STC creation and assignment process.
When Staying With Instant Gas Can Still Make Sense
Instant gas has several characteristics that a heat pump does not reproduce exactly. For some properties, replacing like-for-like can remain a practical option.
Ground Space Is Extremely Limited
A compact wall-mounted continuous-flow unit can suit properties where there is no practical location for a heat-pump storage cylinder.
Continuous Delivery Is a Priority
Correctly sized instant gas keeps heating water while demand continues. A heat pump instead depends on available stored hot water and recovery.
A Simple Replacement Matters Most
Where the existing gas service and installation are suitable, another instant gas system can involve fewer service and location changes than converting technologies.
How an Instant-Gas-to-Heat-Pump Conversion Works
Choose the Heat Pump
Size the system around household demand, usable storage, recovery, noise, controls and electrical requirements.
Choose the Tank Position
Confirm physical space, base, airflow, access, drainage and the plumbing route from the existing services.
Disconnect Instant Gas
The old continuous-flow appliance is isolated and removed, with its gas connection appropriately dealt with.
Install New Services
Plumbing, valves, drainage and the required electrical supply are completed for the new heat pump.
Commission & Test
The tank is filled and the system is tested and configured for normal household use.
Complete STC Requirements
Where eligible, the required STC documentation and assignment process are completed.
Instant Gas to Heat Pump Hot Water FAQs
Can you replace instant gas hot water with a heat pump?
Yes. The main difference is that instant gas is normally a compact continuous-flow appliance with no storage cylinder, while a heat pump needs a tank, suitable installation area, electrical supply, drainage and enough stored capacity and recovery for the household.
Is it worth changing from instant gas to heat pump hot water?
It can be attractive for households wanting to reduce gas use, use rooftop solar for water heating or move toward electric appliances. Tank space, conversion cost, household demand and the change from continuous-flow to stored hot water should all be considered.
Where does the heat-pump tank go?
The new storage cylinder does not have to occupy the exact wall position used by the old gas heater. A suitable ground-level position can be selected based on plumbing distance, airflow, drainage, electrical access, noise and future service access.
Will I still have endless hot water with a heat pump?
Heat pumps operate differently from continuous-flow gas. They store a finite amount of heated water and then recover that storage after use. Correct tank sizing and recovery performance therefore become important for households used to long or back-to-back hot-water use.
Can I use the existing hot and cold water pipes?
Existing water services can often form part of the conversion, but pipework may need to be extended or redirected because the heat-pump tank may be installed in a different position from the old wall-mounted instant gas unit.
What happens to the gas line?
The gas connection serving the old instant-gas appliance needs to be appropriately isolated or altered. The property's main gas supply can remain if other gas appliances are still connected.
Can I disconnect gas completely after changing to heat pump?
If hot water is the property's last remaining gas appliance, changing to heat pump can create an opportunity to consider whether the broader gas supply is still required. Other remaining gas appliances need to be considered separately.
Can LPG instant gas be replaced with a heat pump?
Yes. LPG continuous-flow hot water can be replaced by a heat pump. The LPG hot-water connection is removed from use while the new heat pump requires suitable electrical, plumbing and storage-tank arrangements.
Does an instant-gas-to-heat-pump conversion need electrical work?
The selected heat pump requires an appropriate electrical connection. The final electrical work depends on the exact system, the new tank position and the property's existing electrical infrastructure.
Is heat pump hot water useful with rooftop solar?
It can be. Heat pumps use electricity and many can be scheduled around daylight hours, allowing rooftop solar generation to contribute to heating the stored water where household demand and the selected system allow.
Can I get STCs when replacing instant gas with a heat pump?
An eligible air-source heat pump may qualify when the exact listed model and completed installation satisfy the current STC requirements. The previous appliance being instant gas does not by itself prevent the new heat pump from qualifying.
What heat-pump size replaces a 26L instant gas unit?
There is no direct litres-per-minute to storage-litres conversion. A 26L/min continuous-flow rating describes instantaneous flow capacity, while a heat pump needs to be selected using household occupancy, bathrooms, peak demand, usable stored volume and recovery performance.
Ready to Compare Instant Gas Against Heat Pump?
Start by checking whether the property has a suitable location for a heat-pump storage tank, then compare capacity, recovery, electrical requirements and installed price. If continuous-flow gas still suits the property better, compare JR's current instant-gas range instead.