How to Choose a Replacement Hot Water System

Jun 4, 2026

Choosing a replacement hot water system depends on your current unit, household size, energy source, available space, budget and daily hot water demand. The best replacement is not always the same brand or the cheapest model. It is the system that matches your home, existing connections, tank size or flow rate requirements and long-term hot water needs.

At Hot Water Outlet, you can compare hot water systems online, including electric hot water systems, heat pump hot water systems, gas hot water systems, instant gas hot water systems, instant electric hot water systems and common valves, pipework and fittings.

Quick Answer: What Is the Best Replacement Hot Water System?

The best replacement hot water system is the one that suits your existing setup, household demand, available energy source and installation location.

As a general guide:

Replace an old electric storage system with another electric hot water system if you want a straightforward like-for-like option.
Compare heat pump hot water systems if you are replacing electric storage and want an efficient electric alternative.
Replace an old gas storage unit with a gas hot water system if you want a traditional gas tank-style replacement.
Compare instant gas hot water systems if your home has natural gas or LPG and you want continuous flow gas hot water.
Choose instant electric hot water systems only for suitable point-of-use applications where the electrical requirements and flow demand match the product.
Check whether you need valves, pipework and fittings as part of the replacement order.

For most buyers, the easiest starting point is to identify the current hot water system, then compare replacement options by system type, size, energy source, dimensions, connection positions and product specifications.

Step 1: Identify Your Current Hot Water System

Before choosing a replacement, start with the system you already have. The current unit tells you a lot about what may be suitable.

Look for the data plate or product label on the unit. It may show:

Brand
Model number
Tank capacity
Flow rate
Energy source
Natural gas or LPG type
Power rating
Pressure rating
Manufacturing date
Indoor or outdoor suitability
Serial number
Product code

This information helps you compare similar replacement models and avoid ordering a system that does not match the property.

If the current system has worked well for years and household demand has not changed, a similar type and size may be a practical starting point. If the current system has always struggled, runs out often or no longer suits the home, it may be worth comparing other options before replacing it.

Step 2: Decide Whether You Want Like-for-Like or an Upgrade

There are two main ways to approach hot water replacement.

A like-for-like replacement means choosing a similar system type, similar size and similar energy source to the old unit. This can be practical when the existing setup works well and the household demand has not changed.

An upgrade means changing size, brand, system type or energy source. This may be worth considering if the old system no longer suits the home, you are renovating, household size has changed or you want to compare more efficient options.

Like-for-Like Replacement

A like-for-like replacement may suit if:

The old system supplied enough hot water
Household size has not changed
Bathroom count has not changed
The current location still works
The energy source is staying the same
The system type still suits the home
You want a straightforward replacement path

For example, an old electric storage tank may be replaced with another electric storage system. An old gas storage unit may be replaced with another gas storage system. An old instant gas unit may be replaced with another instant gas unit with a similar flow rate.

Upgrading or Changing System Type

Changing system type may be worth comparing if:

The old system often ran out of hot water
More people now live in the home
A bathroom has been added
A renovation is changing hot water demand
You want to compare heat pump options
You want to move from gas storage to instant gas
You want to replace standard electric storage with a heat pump
The current system location is no longer suitable
The old unit is oversized or undersized

Changing system type can involve extra plumbing, gas or electrical requirements, so it should be planned carefully with licensed tradespeople.

Step 3: Match the Replacement to Your Energy Source

Your available energy source will narrow your choices quickly.

Most homes will be replacing one of these:

Electric storage hot water
Heat pump hot water
Gas storage hot water
Instant gas hot water
Instant electric hot water
Solar hot water with electric or gas boosting

If your home already has electricity only, compare electric hot water systems and heat pump hot water systems.

If your home already has natural gas or LPG, compare gas hot water systems and instant gas hot water systems.

If you are replacing a compact point-of-use system, compare instant electric hot water systems only if the intended use and electrical requirements are suitable.

The easiest replacement is often the one that keeps the same energy source, but it is still worth comparing the main options before ordering.

Step 4: Choose the Right System Type

Hot water replacement is not just about brand. The system type matters more.

Electric Hot Water Replacement

An electric hot water system may be the right replacement if your old unit is an electric storage tank and you want a familiar tank-style setup.

Electric storage replacement may suit:

Homes without gas
Existing electric storage systems
Rental properties with electric tanks
Townhouses and units with suitable space
Like-for-like replacement projects
Buyers wanting a broad range of tank sizes

Before replacing electric storage, check the current tank capacity, recovery rate, dimensions, power requirements, pressure rating and connection positions.

Heat Pump Hot Water Replacement

A heat pump hot water system may be worth comparing if you are replacing old electric storage and want an efficient electric option.

Heat pump replacement may suit:

Homes replacing older electric storage
Households wanting efficient electric hot water
Properties with suitable outdoor space
Locations with enough airflow
Homes where noise considerations can be managed
Renovations where the system location can be planned properly

Before choosing a heat pump, check tank size, product dimensions, airflow requirements, noise rating, electrical requirements, location suitability and household demand.

Gas Storage Hot Water Replacement

A gas hot water system may be the right replacement if your current system is gas storage and you want a traditional stored hot water option.

Gas storage replacement may suit:

Homes already using natural gas or LPG
Existing gas storage systems
Like-for-like gas replacements
Properties where a storage tank is still preferred
Households where tank capacity and recovery rate suit demand

Before replacing gas storage, confirm natural gas or LPG, tank capacity, recovery rate, pressure rating, dimensions, connection positions and location suitability.

Instant Gas Hot Water Replacement

An instant gas hot water system may suit homes with natural gas or LPG where continuous flow hot water is preferred.

Instant gas replacement may suit:

Existing instant gas systems
Homes replacing old gas storage with continuous flow
Properties with suitable gas supply
Homes where a large storage tank is not ideal
Households where the correct flow rate can be matched to demand

Before choosing instant gas, check natural gas or LPG, flow rate in L/min, controller compatibility, dimensions, connection positions, gas supply and product specifications.

Instant Electric Hot Water Replacement

An instant electric hot water system is generally suited to specific point-of-use applications where the product, electrical requirements and flow demand match the intended use.

Instant electric replacement may suit:

Compact point-of-use hot water
Small applications where suitable
Specific fixtures requiring local hot water
Projects where storage is not practical

Before choosing instant electric, check the electrical requirements carefully. These systems are not automatically suitable for every whole-home hot water application.

Step 5: Choose the Right Size

Sizing is one of the most important parts of replacing a hot water system.

Storage systems are measured by tank capacity in litres. This includes electric storage, gas storage and heat pump hot water systems.

Instant gas systems are measured by flow rate in L/min. They do not store hot water in a large tank, so sizing works differently.

When choosing a replacement size, consider:

Number of people in the home
Number of bathrooms
Number of showers per day
Bath use
Laundry use
Kitchen use
Whether hot water is used at the same time
Current tank size or flow rate
Whether the old system ran out
Future household changes
Renovation plans
Recovery rate
Available space

Do not automatically choose the same size as the old system. The old unit is a useful starting point, but the right replacement depends on how the home uses hot water now.

What Size Replacement for Electric Storage?

Electric storage systems are usually replaced by comparing tank capacity, recovery rate and dimensions.

If the old electric tank worked well, a similar capacity may be a practical starting point. If the old tank ran out regularly, compare a larger tank or a heat pump option with suitable capacity.

Check:

Current tank capacity
Household demand
Recovery rate
Physical dimensions
Power requirements
Connection positions

What Size Replacement for Heat Pump Hot Water?

Heat pumps are also sized by tank capacity, but location matters as much as size.

A heat pump replacement should be chosen by:

Tank capacity
Household demand
Outdoor space
Airflow
Noise rating
Unit dimensions
Electrical requirements
Product specifications

A heat pump with the right tank size still may not be suitable if the location lacks airflow or space.

What Size Replacement for Gas Storage?

Gas storage systems are selected by tank capacity and recovery rate. A similar tank capacity may suit if the existing unit worked well.

Check:

Current tank capacity
Gas type
Recovery rate
Number of occupants
Number of bathrooms
Dimensions
Connection positions
Pressure rating

What Size Replacement for Instant Gas?

Instant gas systems are selected by flow rate in L/min.

Common flow rate comparisons include:

Instant Gas Flow Rate	Common Use Case	Check Before Ordering
16 L/min	Smaller homes or lower demand	Gas type, number of outlets and usage pattern
20 L/min	Medium household demand	Bathrooms, showers and simultaneous use
26 L/min	Larger homes or higher demand	Gas type, peak demand and product suitability

The right flow rate depends on real household demand, not just the number of people in the home.

Step 6: Check Dimensions and Location

A replacement hot water system must physically fit the available space. Do not assume a new model will fit because the capacity looks similar.

Before ordering, check:

Height
Width
Depth
Weight
Clearance requirements
Access for delivery
Existing base or wall location
Indoor or outdoor suitability
Ventilation or airflow needs
Drainage
Distance from windows, doors and boundaries where relevant

This is especially important when changing system type. A heat pump may need more airflow than an old electric tank. An instant gas system may need a different wall location than a gas storage tank. A larger storage tank may not fit where the old tank was.

Step 7: Check Connection Positions

Connection positions can make or break a replacement choice.

Check the current system and compare it with the new product’s specifications. Look for:

Cold water inlet position
Hot water outlet position
Gas connection position if gas
Electrical connection position if electric
Relief valve position
Drainage
Controller wiring if instant gas
Existing pipework alignment

A system with the right capacity may still require extra work if the connections do not line up well. This is why product specifications matter before ordering.

Step 8: Confirm Natural Gas or LPG

If you are replacing a gas hot water system, gas type is one of the most important checks.

Natural gas and LPG hot water systems are not interchangeable.

Before ordering gas hot water, confirm whether the property uses:

Natural gas
LPG bottles
Bulk LPG
Existing natural gas hot water
Existing LPG hot water

Do not guess based on appearance. If you are unsure, ask a licensed gas fitter before ordering.

Choosing the wrong gas type can cause delays, compatibility issues and extra costs.

Step 9: Check Whether You Need Valves, Fittings and Pipework

A replacement hot water system order may need more than the main unit. Depending on the system type, water pressure, age of the existing setup and connection layout, extra parts may be required.

Common items include:

Tempering valves
Pressure relief valves
Duo valves
Non-return valves
Isolation valves
Copper pipework
Fittings
Controller accessories
Thermostats
Elements
Connection parts

Hot Water Outlet has a dedicated range of valves, pipework and fittings to help customers compare common hot water parts and accessories.

Always confirm compatibility before ordering.

Step 10: Compare Brands

Brand can help narrow your choice, but it should not be the only factor. A trusted brand still needs to be the right system type, size, gas type, location and configuration for the property.

Hot Water Outlet lists recognised hot water brands including:

When comparing brands, check:

System type
Tank size or flow rate
Energy source
Gas type
Dimensions
Warranty information
Product specifications
Household suitability
Required accessories

Replacement Options by Current System Type

Replacing an Electric Storage Hot Water System

If your current unit is electric storage, you can compare another electric storage system or consider a heat pump if the property is suitable.

Compare:

Choose electric storage if you want a straightforward replacement. Compare heat pump if you want an efficient electric option and have suitable outdoor space and airflow.

Replacing a Gas Storage Hot Water System

If your current unit is gas storage, you can compare another gas storage system or consider instant gas if continuous flow suits the property.

Compare:

Choose gas storage if you want a traditional tank-style replacement. Compare instant gas if you want continuous flow hot water and the selected flow rate suits the household.

Replacing an Instant Gas Hot Water System

If your current system is instant gas, start by checking the current flow rate and gas type.

Compare:

A similar flow rate may suit if the old system worked well. If it struggled with demand, compare higher-flow options where suitable.

Replacing a Heat Pump Hot Water System

If your current system is a heat pump, compare another heat pump first. Also compare electric storage if a simpler tank-style replacement is preferred.

Compare:

Check the existing tank capacity, airflow, location, dimensions and power requirements before ordering.

Replacing Solar Hot Water

Some homes replace older solar hot water systems with electric storage, heat pump or gas options depending on the property.

Replacement choices may include:

Heat pump hot water
Electric storage hot water
Gas storage hot water
Instant gas hot water where gas is available

Before replacing solar, check the existing booster type, tank location, roof components, plumbing layout, electrical or gas requirements and household demand. A licensed tradesperson should assess the setup before removal or replacement.

Replacement Hot Water System Comparison Table

Current System	Common Replacement Options	Main Things to Check
Electric storage	Electric storage or heat pump	Tank size, power requirements, dimensions, airflow if heat pump
Gas storage	Gas storage or instant gas	Natural gas or LPG, tank size, flow rate, connection positions
Instant gas	Instant gas	Gas type, flow rate, controller compatibility, dimensions
Heat pump	Heat pump or electric storage	Tank size, airflow, noise rating, location, power requirements
Solar hot water	Heat pump, electric, gas or instant gas	Booster type, location, plumbing layout, energy source

When Should You Replace a Hot Water System?

You may need to consider replacement if:

The tank is leaking
Hot water runs out quickly
Water from hot taps looks rusty
The unit is old and unreliable
The system makes unusual noises
Repairs are becoming uneconomical
The current system no longer suits the household
You are renovating
You are adding another bathroom
You want to compare a different system type
A licensed tradesperson has recommended replacement

Not every problem means the system must be replaced. Some issues may relate to valves, thermostats, elements, controllers or other components. If you are unsure, speak with a licensed plumber, gas fitter or electrician before ordering.

Replacement Hot Water for Families

Family homes usually need careful sizing because hot water use is higher and more frequent.

For families, compare:

Number of occupants
Number of bathrooms
Shower habits
Bath use
Morning and evening peak demand
Kitchen hot water use
Laundry use
Whether multiple outlets are used at once
Current system performance
Tank size or flow rate

A family replacing a small electric tank may need a larger electric system or a heat pump. A family replacing gas storage may compare larger gas storage or instant gas with a suitable flow rate.

Replacement Hot Water for Small Homes

Small homes, units and townhouses may have lower demand, but sizing still matters.

For small homes, compare:

Available space
Existing system type
Number of occupants
Number of bathrooms
Shower habits
Energy source
Tank capacity or flow rate
Indoor or outdoor location
Access and delivery

A compact electric storage system, smaller heat pump, lower-flow instant gas unit or suitable instant electric unit may be worth comparing depending on the setup.

Replacement Hot Water for Rental Properties

Rental properties need a practical replacement that suits the property and likely tenant demand.

For rentals, compare:

Current system type
Number of bedrooms
Number of bathrooms
Likely tenant use
Product availability
Brand recognition
Warranty information
Ease of replacement
Required valves and fittings
Delivery access

A like-for-like replacement may often be practical for rental properties, but it is still worth checking whether the current size and system type suit the property.

Replacement Hot Water for Renovations

Renovations can change hot water demand. If you are adding a bathroom, upgrading a kitchen or changing the laundry, the old hot water system may no longer be the best match.

For renovations, consider:

Future number of bathrooms
Larger bath or shower upgrades
Kitchen layout changes
Laundry upgrades
System location changes
Energy source changes
Tank size or flow rate needs
Required valves, pipework and fittings
Whether the system should be moved
Whether a heat pump or instant gas option suits the new layout

Plan around the finished home, not the current home.

Common Mistakes When Choosing a Replacement Hot Water System

Replacing With the Same System Without Checking Demand

The old system may not suit the home anymore. If household size or usage has changed, compare updated options.

Choosing by Price Alone

A cheaper unit is not good value if it is the wrong size, gas type, flow rate or connection layout.

Buying the Wrong Gas Type

Natural gas and LPG models are different. Always confirm the gas type before ordering.

Ignoring Dimensions

A system may have the right capacity but still not fit the available location.

Comparing Litres and L/min Incorrectly

Storage systems are measured by tank capacity in litres. Instant gas systems are measured by flow rate in L/min.

Forgetting Heat Pump Location Requirements

Heat pumps need suitable space and airflow. They should not be chosen by tank size alone.

Forgetting Valves and Accessories

Some replacements need valves, fittings or pipework. Check the full order, not just the main unit.

Assuming DIY Replacement Is Suitable

Hot water replacement can involve plumbing, gas and electrical work. These tasks should be completed by appropriately licensed tradespeople.

Replacement Hot Water Buyer Checklist

Before ordering a replacement hot water system online, check:

Current brand and model
Current system type
Current tank capacity or flow rate
Natural gas, LPG or electricity
Household size
Number of bathrooms
Daily hot water demand
Whether the current system runs out
Desired system type
Tank capacity if storage
Flow rate in L/min if instant gas
Recovery rate
Product dimensions
Connection positions
Indoor or outdoor suitability
Heat pump airflow requirements if relevant
Noise rating if choosing heat pump
Power requirements
Gas requirements
Required valves
Required fittings
Delivery access
Warranty information
Product specifications

Can You Order a Replacement Hot Water System Online?

Yes. Hot Water Outlet allows customers to compare and order supply-only hot water systems and accessories online. You can browse by system type, brand, capacity, flow rate, gas type and product specifications.

Hot Water Outlet sells supply-only products and may help organise quotes from reputable installers where appropriate. Hot water installation, gas fitting, electrical work and plumbing connections should be handled by appropriately licensed tradespeople.

Before ordering online, make sure you have checked the current system details and compared the replacement specifications carefully.

Compare Replacement Hot Water Systems Online

Hot Water Outlet makes it easier to compare replacement hot water systems online by type, brand, size, energy source and household suitability.

Start with:

FAQs About Replacement Hot Water Systems

What is the best replacement hot water system?

The best replacement hot water system is the one that matches your current setup, household demand, energy source, available space and product requirements. Start by checking your current system type, size, gas type or power requirements, then compare suitable replacement options.

Should I replace my hot water system with the same type?

Replacing with the same type may be practical if the old system worked well and household demand has not changed. If the old system often ran out, was expensive to run or no longer suits the home, compare other system types before ordering.

Can I replace electric hot water with a heat pump?

A heat pump may be worth comparing if you are replacing electric storage and have suitable outdoor space, airflow and household demand. Check tank size, dimensions, noise rating and product specifications before ordering.

Can I replace gas storage with instant gas?

Some homes may be able to replace gas storage with instant gas, but suitability depends on gas type, gas supply, flow rate needs, location and connection requirements. Speak with a licensed gas fitter if you are unsure.

What size replacement hot water system do I need?

The right size depends on household size, number of bathrooms, shower habits, bath use, laundry use and kitchen use. Storage systems are measured in litres. Instant gas systems are measured by flow rate in L/min.

How do I know if my replacement needs natural gas or LPG?

Check the current system label, gas bottles, gas meter or property gas supply. Natural gas and LPG systems are not interchangeable. If you are unsure, ask a licensed gas fitter before ordering.

Do I need valves and fittings with a replacement hot water system?

Some replacements require valves, pipework or fittings depending on the system type, pressure rating and connection layout. Browse valves, pipework and fittings and confirm compatibility before ordering.

Can I replace a hot water system myself?

No. Hot water systems involve plumbing, gas and electrical work that should be completed by appropriately licensed tradespeople. Hot Water Outlet sells supply-only hot water systems and accessories online, and may help organise quotes from reputable installers where appropriate.

What should I check before ordering a replacement hot water system online?

Check the current system type, tank size or flow rate, gas type, power requirements, dimensions, connection positions, pressure rating, required valves, delivery access, warranty information and product specifications.

Is it better to repair or replace a hot water system?

That depends on the age of the system, the fault, parts availability, repair cost and whether the current unit still suits the household. If repair costs are high or the system is old and unreliable, replacement may be worth comparing.

Find the Right Replacement Hot Water System Online

The right replacement hot water system should suit your home, energy source, available space, household demand and existing setup. Before ordering, compare the system type, size, brand, gas type, flow rate, recovery rate, dimensions, connection positions and any required accessories.

Browse hot water systems online with Hot Water Outlet to compare electric, gas, instant gas, instant electric, heat pump and replacement hot water options from trusted brands.

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