Rheem MPi-325 Series II Heat Pump Hot Water System

The Rheem MPi-325 Series II Heat Pump Hot Water System is available online from Hot Water Outlet as a supply-only heat pump water heater with metro delivery available in selected areas Australia wide.

Customers can purchase the Rheem MPi-325 Series II as a supply-only heat pump hot water system and request assistance arranging installation quotes after purchase through licensed local installers in selected metro regions.

The Rheem MPi-325 Series II is a 325L heat pump hot water system designed for small to medium electric water heater replacement. With 325L storage capacity, 180L boost capacity, 3.6kW backup element, R134a refrigerant, two-piece system configuration, and suitability for up to 5 people under Rheem’s stated assumptions, it is a practical heat pump upgrade option for households wanting to reduce water heating energy use compared with standard electric storage.

About the Rheem MPi-325 Series II Heat Pump

The Rheem MPi-325 Series II Heat Pump uses environmental heat pump technology to absorb heat from the surrounding air and transfer it into stored water.

Instead of relying only on direct electric element heating, the system uses a refrigeration cycle to heat water more efficiently. Rheem positions the MPi-325 as using around one third of the energy of a standard electric water heater under suitable conditions, with potential water heating energy savings of up to 65% in Zone 3 when replacing an electric water heater of similar size.

The MPi-325 is recommended for replacement of small to medium electric water heaters across climate Zones 1 to 4. It is also designed to work day and night because it does not rely on roof-mounted solar collectors or direct sunlight.

Buy Rheem MPi-325 Supply Only

Order the Rheem MPi-325 Series II Heat Pump Hot Water System online from Hot Water Outlet with metro delivery available in selected areas across Australia.

This option is ideal if you already have a licensed plumber, electrician or installer arranged and only need the unit supplied.

The supply-only product price includes the hot water system itself.

Installation, old system removal, disposal, valve kits, electrical work, plumbing alterations, drainage changes, compliance upgrades and additional site requirements are not included unless separately quoted.

Supply-only is best for customers searching for:

• Rheem MPi-325 price

• Rheem MPi-325 Series II heat pump for sale

• Rheem 551325 heat pump hot water system

• Rheem MPi 325L heat pump supply only

• 325L heat pump hot water system supply only

• Rheem heat pump water heater

• Rheem MPi heat pump replacement

• R134a heat pump hot water system

Installation Quotes Available After Purchase

Hot Water Outlet does not directly provide installation services.

After purchasing the Rheem MPi-325 Series II Heat Pump Hot Water System, customers in selected metro areas may request assistance arranging installation quotes through licensed local plumbers and electricians.

Installation quote availability depends on:

• service location

• installer availability

• existing system type

• outdoor location suitability

• drainage suitability

• electrical connection requirements

• plumbing suitability

• compliance requirements

Additional installation costs may apply for:

• valve upgrades

• electrical upgrades

• drainage changes

• pipework changes

• difficult access

• concrete bases

• old system removal

• disposal

• compliance upgrades

Rheem MPi-325 Delivery Brisbane

Hot Water Outlet offers metro delivery for the Rheem MPi-325 Series II Heat Pump Hot Water System in selected Brisbane areas.

Customers can order online and request assistance arranging installation quotes after purchase where available.

Rheem MPi-325 Delivery Gold Coast

Hot Water Outlet offers metro delivery for the Rheem MPi-325 Series II Heat Pump Hot Water System in selected Gold Coast service areas.

Customers can purchase online and organise installation separately or request help arranging installation quotes after purchase.

Rheem MPi-325 Delivery Sydney

Hot Water Outlet offers metro delivery for the Rheem MPi-325 Series II Heat Pump Hot Water System in selected Sydney metro areas.

Customers can order online with installation quote assistance available after purchase in selected locations.

Rheem MPi-325 Delivery Melbourne

Hot Water Outlet offers metro delivery for the Rheem MPi-325 Series II Heat Pump Hot Water System in selected Melbourne metro areas.

Customers can purchase the system online and request help arranging installation quotes after delivery.

Is the Rheem MPi-325 Right for Your Home?

The Rheem MPi-325 Series II Heat Pump may be suitable if you are replacing a small to medium electric storage hot water system and want a heat pump option from one of Australia’s most recognised hot water brands.

It is commonly suited to homes where a standard electric water heater is being replaced, especially where the property has suitable outdoor space, airflow, drainage and electrical supply for a heat pump installation.

Rheem lists the MPi-325 as suitable for up to 5 people under its stated usage assumptions. Real-world suitability depends on shower length, hot water usage, tariff setup, climate, installation location, airflow, drainage, electrical supply and household hot water habits.

This system may suit you if:

• you are replacing an existing electric hot water system

• you want a 325L heat pump hot water system

• your household has up to 5 people under Rheem’s stated assumptions

• you want a heat pump designed for small to medium electric water heater replacement

• you want a system that does not rely on direct sunlight

• you want a 3.6kW boost element for backup support

• you want a two-piece heat pump system configuration

• your property has suitable airflow, drainage and installation space

• your electrical setup can support the required circuit

• you prefer supply-only purchase flexibility

Extra work may be required if:

• the system is being moved to a new location

• the existing electrical connection does not suit the heat pump

• a licensed electrician is required to alter or upgrade the circuit

• existing valves are old, missing or non-compliant

• extra pipework or drainage changes are needed

• access is restricted

• a compliant base, tray, drainage or insulation is required

• the old system needs additional removal or disposal work

• the installation location has poor airflow or unsuitable clearances

• the existing setup does not suit a heat pump installation

Key Features of the Rheem MPi-325 Series II

• 325L heat pump hot water system

• Model 551325

• Suitable for up to 5 people under Rheem’s stated usage assumptions

• Recommended for small to medium electric water heater replacement

• Suitable for climate Zones 1 to 4

• Uses heat from surrounding air to heat water

• Does not rely on direct sunlight or roof-mounted solar panels

• Multi-pass heating technology

• Constant recovery design to help minimise energy use

• Two-piece system configuration

• Designed for one plumber installation where site conditions allow

• COP of 3.6 at 19°C under stated test conditions

• Can save up to 65% on water heating energy consumption in Zone 3 compared with an electric water heater under Rheem’s stated conditions

• 3.6kW boost element

• Frost protection support

• LED display for operating status

• R134a refrigerant

• 800W rated heat pump power input

• 15A recommended electrical circuit

• 52 dB(A) listed noise level at 1 metre under test conditions

• Eligible for STCs where requirements are met

• May be eligible for additional incentives in some states

• Manufactured in Australia

• 5-year cylinder supply warranty under Rheem warranty terms

• 3-year cylinder labour warranty under Rheem warranty terms

• 2-year sealed system supply and labour warranty under Rheem warranty terms

• 1-year parts supply and labour warranty under Rheem warranty terms

Quick Specs

Brand: Rheem
Range: Rheem MPi Series II Heat Pump
Product: Rheem MPi-325 Series II Heat Pump
Model: 551325
System Type: Heat Pump Hot Water System
Storage Capacity: 325L
Boost Capacity: 180L
Recommended Household Size: Up to 5 people under Rheem’s stated usage assumptions
Rated Heat Pump Power Input: 800W
Element Rating: 3.6kW
Recommended Electrical Circuit: 15A
Refrigerant: R134a
COP: 3.6 at 19°C under stated test conditions
Noise Level: 52 dB(A) at 1 metre under test conditions
Tank Height: 1631mm
Tank Width: 863mm
Tank Depth: 638mm
Heat Pump Module Weight: 42kg
Tank Weight Empty: 88kg
Water Connections: Rp 3/4
TPR Valve Setting: 1000 kPa
Expansion Control Valve Setting: 850 kPa
Max Mains Supply Pressure With ECV: 680 kPa
Max Mains Supply Pressure Without ECV: 800 kPa
Government Incentive Eligibility: STCs where requirements are met
Cylinder Warranty: 5 years subject to Rheem warranty terms
Cylinder Labour Warranty: 3 years subject to Rheem warranty terms
Sealed System Warranty: 2 years supply and labour subject to Rheem warranty terms
Parts Warranty: 1 year supply and labour subject to Rheem warranty terms

Heat Pump Performance

The Rheem MPi-325 Series II is designed to adjust performance depending on ambient air temperature, humidity and incoming water temperature.

Under Rheem’s listed test conditions, performance is shown as:

At 7°C ambient air temperature and 86% relative humidity:

• Average heating capacity of 1.5kW

• Recovery rate of 28 L/hr at a 45°C rise

• Average COP of 2.8

At 19°C ambient air temperature and 65% relative humidity:

• Average heating capacity of 1.9kW

• Recovery rate of 36 L/hr at a 45°C rise

• Average COP of 3.6

At 33°C ambient air temperature and 35% relative humidity:

• Average heating capacity of 2.5kW

• Recovery rate of 47 L/hr at a 45°C rise

• Average COP of 4.2

At 33°C ambient air temperature and 59% relative humidity:

• Average heating capacity of 2.6kW

• Recovery rate of 50 L/hr at a 45°C rise

• Average COP of 4.5

Actual performance can vary depending on local climate, time of day, water temperature, installation location, airflow, household use and tariff setup.

Multi-Pass Heating Technology

The Rheem MPi-325 Series II uses multi-pass heating, where water passes through the heat exchanger multiple times during the heating process.

This design helps heat water isothermally and supports steady, efficient hot water production. It is designed to work with the system’s constant recovery approach, helping optimise heating while reducing energy use compared with standard electric storage.

3.6kW Boost Element

The Rheem MPi-325 includes a 3.6kW boost element.

The boost element provides frost protection and backup heating support during very cold conditions. It is designed to help ensure hot water remains available when heat pump operation needs support.

This can be useful for households that want heat pump efficiency most of the time, with electric backup available when required.

Two-Piece System Configuration

The Rheem MPi-325 Series II uses a two-piece configuration with a separate tank and heat pump module.

This setup can help with installation flexibility and allows single plumber installation where the site conditions are suitable. The installation location still needs proper clearances, airflow, drainage, access and electrical connection.

The two-piece design also means the site needs to be checked carefully before ordering, especially where access, side clearance, wall clearance or installation area is limited.

Energy Savings Potential

The Rheem MPi-325 Series II is designed to reduce water heating energy use compared with a standard electric water heater.

Rheem lists potential savings of up to 65% in Zone 3 when replacing an electric water heater of similar size under stated modelling conditions.

Actual savings can vary depending on household usage, system size being replaced, electricity tariff, location, climate, hot water demand and installation setup.

Electrical Connection and Tariff Suitability

The Rheem MPi-325 is listed with a 15A recommended electrical circuit and a 3.6kW element rating.

Rheem notes the system is recommended for connection to either a 24-hour continuous tariff or an extended off-peak tariff of at least 16 hours per day, depending on site and replacement conditions.

If replacing an electric water heater greater than 160L, a 24-hour continuous tariff is generally recommended for this heat pump. Customers should confirm electrical and tariff suitability before ordering or installation.

STCs and Incentives

The Rheem MPi-325 Series II may be eligible for Small-scale Technology Certificates where requirements are met.

Eligibility and value can vary depending on installation location, climate zone, product model, installation date, installer requirements and program rules. Some states may also offer additional incentives where conditions are met.

Any rebate, STC discount or incentive should be confirmed before ordering or installation.

Common Uses

The Rheem MPi-325 Series II Heat Pump can be suitable for:

• electric hot water system replacement

• small to medium electric water heater replacement

• heat pump hot water upgrades

• family homes

• townhouses

• rental properties

• investment properties

• homes with up to 5 people under Rheem’s stated assumptions

• homes wanting lower energy use than standard electric storage

• homes where roof-mounted solar hot water may not be suitable

• properties needing a 325L heat pump hot water system

Frequently Asked Questions

Can I buy the Rheem MPi-325 supply only?

Yes. You can buy the Rheem MPi-325 Series II as a supply-only product if you already have a licensed installer arranged.

Does Hot Water Outlet install heat pump hot water systems?

No. Hot Water Outlet does not directly provide installation services. Customers may request assistance arranging installation quotes after purchase in selected metro areas.

Can I get an installation quote after purchasing?

Yes. Customers in selected metro areas may request help arranging installation quotes through licensed local installers after purchasing the system.

Is delivery available Australia wide?

Metro delivery is available in selected service areas across Australia. Delivery availability may vary depending on location and product type.

What is the model number for the Rheem MPi-325?

The Rheem MPi-325 Series II model number is 551325.

What is the storage capacity?

The Rheem MPi-325 has a 325L storage capacity.

What is the boost capacity?

The Rheem MPi-325 has a listed 180L boost capacity.

How many people is the Rheem MPi-325 suitable for?

Rheem lists the MPi-325 as suitable for up to 5 people under stated usage assumptions. Actual suitability depends on shower length, hot water usage, tariff setup, climate and household habits.

What refrigerant does the Rheem MPi-325 use?

The Rheem MPi-325 uses R134a refrigerant.

What is the COP of the Rheem MPi-325?

The Rheem MPi-325 has a listed average COP of 3.6 at 19°C under stated test conditions.

What is the recovery rate?

At 19°C ambient air temperature and 65% relative humidity, the Rheem MPi-325 is listed with a recovery rate of 36 L/hr at a 45°C rise under stated test conditions.

What size backup element does the Rheem MPi-325 have?

The Rheem MPi-325 has a listed 3.6kW boost element.

What electrical circuit does the Rheem MPi-325 need?

The Rheem MPi-325 is listed with a 15A recommended electrical circuit. Electrical suitability should be confirmed before installation.

Does the Rheem MPi-325 need direct sunlight?

No. The Rheem MPi-325 uses heat from the surrounding air and does not rely on direct sunlight or roof-mounted solar panels.

Is the Rheem MPi-325 suitable for replacing an electric hot water system?

Yes. The Rheem MPi-325 is recommended for replacement of small to medium electric water heaters in climate Zones 1 to 4 where the property and household demand suit the system.

Can the Rheem MPi-325 reduce running costs?

Yes. Rheem lists potential water heating energy savings of up to 65% in Zone 3 compared with an electric water heater of similar size under stated modelling conditions. Actual savings depend on location, household usage, tariff setup, installation conditions and the system being replaced.

Is the Rheem MPi-325 eligible for STCs?

The Rheem MPi-325 may be eligible for STCs where requirements are met. Eligibility and value can vary depending on location, installation year, product model, installer requirements and program rules.

What is the noise level of the Rheem MPi-325?

The Rheem MPi-325 is listed with a noise level of 52 dB(A) at 1 metre under test conditions. Installed noise can vary depending on walls, nearby structures, clearances and site layout.

What is the warranty on the Rheem MPi-325?

Rheem lists the MPi-325 with a 5-year cylinder supply warranty, 3-year cylinder labour warranty, 2-year sealed system supply and labour warranty, and 1-year supply and labour warranty on all other parts, subject to Rheem warranty terms and conditions.

What is the difference between the Rheem MPi-325 and AmbiPower 280e?

The Rheem MPi-325 is a 325L Series II heat pump with a two-piece configuration, R134a refrigerant, 3.6kW boost element and up to 5-person suitability. The AmbiPower 280e is a newer 280L heat pump using R290 natural refrigerant, with plug-in or hardwired model options depending on the selected variant.

Tempering Valve and Element Information

*Element size information:
All electric hot water units are supplied as standard with a 3.6kW element unless otherwise stated on the product page, invoice, or order confirmation.

If a different element configuration is requested, such as 1.8kW or 2.4kW, the hot water unit may still arrive with the standard 3.6kW element fitted from the manufacturer. The requested 1.8kW or 2.4kW element will be supplied separately with the order for installation by a suitably licensed electrical contractor or licensed electrical licence holder.

Any element changeover, electrical connection, disconnection, wiring, testing, or modification must be carried out by a licensed electrical contractor or licensed electrical licence holder. Elements must not be changed, connected, modified, or tested by an unlicensed person.

Alternative elements supplied for non-standard configurations may be generic replacement elements and may not be the same brand as the hot water unit unless specifically stated. Generic elements are supplied to suit the requested element size and electrical configuration, but final suitability must be checked by the licensed installer before installation.

1.8kW and 2.4kW elements supplied separately with a hot water unit include a 12-month supply-only parts warranty from the date of purchase, provided the element has been correctly installed by a licensed electrical contractor or licensed electrical licence holder and used under normal operating conditions.

This element warranty covers the replacement supply of the element only. It does not include labour, call-out fees, electrical work, plumbing work, fault finding, removal, reinstallation, testing, travel, downtime, damage caused by incorrect installation, or any other associated costs. Warranty may be declined where the element has been incorrectly installed, dry-fired, modified, damaged, connected to incorrect voltage or wiring, affected by power issues, used in unsuitable water conditions, or installed by an unlicensed person.

Proof of purchase, installer details, electrical licence details, photos, and/or return of the faulty element may be required before a warranty claim is approved.

**Tempering valve information:
Where a hot water system is capable of delivering water above 50°C, a compliant tempering valve must be installed to control the temperature delivered to personal hygiene fixtures such as showers, baths, basins, and bathroom outlets. This helps reduce the risk of scalding and assists with meeting plumbing compliance requirements.

A tempering valve blends hot and cold water to deliver a safer controlled outlet temperature to required fixtures. The hot water unit itself may store water at a higher temperature, but the water delivered to personal hygiene outlets must be controlled where required by plumbing regulations.

If your property already has a suitable, compliant tempering valve installed, your licensed plumber can assess whether it is appropriate for use with the new hot water system. Existing valves may not always be suitable due to age, condition, compliance requirements, valve type, location, or system compatibility.

If a compliant tempering valve is not already installed, or if the existing valve is unsuitable, one must be supplied and installed by a licensed plumber as part of the hot water installation.

Tempering valves are not automatically included with every supply-only hot water unit unless specifically selected, listed as included, or purchased as part of a suitable valve kit. If a tempering valve is required, please purchase the appropriate valve kit with your order or arrange for your licensed installer to supply and install the correct tempering valve on site.

It is the customer’s responsibility to ensure the installation is completed by appropriately licensed trades and that all required valves, fittings, electrical work, plumbing work, and compliance requirements are allowed for as part of the installation.

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Important Note

Product suitability can vary by property, existing services, energy source, gas type, available space, connection points, pressure requirements and local compliance requirements. Always check product specifications carefully and confirm the selected hot water system, valves, fittings and accessories are suitable for your property before ordering.

Standard Delivery: 2–8 business days

Express Delivery: 1–4 business days

90% of products are delivered the next business day where stock, postcode eligibility and freight availability allow.

Delivery timeframes are estimates and may vary by product, stock location, delivery postcode, carrier availability and order timing. Wet weather, storms, flooding or unsafe site access may delay delivery and are additional to any advertised or guaranteed freight timeframes.