Solahart Atmos Heat Pump Water Heater: Key Attributes

Key Features


    No roof-mounted solar collectors: Ideal for installations not suitable for traditional solar water heaters.

  •  Eligible for STCs: Solahart Atmos qualifies for Small-Scale Technology Certificates (STCs), helping you reduce the up-front cost of your purchase. (1)

    Energy Efficient: Energy efficient water heating. Solahart Atmos uses less energy than a conventional electric water heater


    Reduced Energy Use: Water heating energy use may be reduced by up to 64% when replacing an electric water heater. (2)


    Electric boosting: Electric booster back-up for hot water in very cold conditions for continuous hot water.




(1) Small-scale Technology Certificates (STCs) are a financial benefit to encourage the installation of solar and heat pump water heaters provided under a Federal Government legislated scheme. STCs financial benefit value is subject to change. Your installation may be eligible. Please refer to for further details.

(2) Energy savings of up to 64% shown is based on Australian Government approved TRNSYS simulation modelling of a Solahart Atmos 325HAV heat pump and using a medium load in Zone 3 and apply when replacing an electric water heater. Any savings will vary depending upon your location, type of Solahart system installed, type of water heater being replaced, hot water consumption and fuel tariff. Maximum financial savings off your hot water bill are achievable when replacing an electric water heater on continuous tariff.

(3) Harsh water regions – the Solahart Warranty may not apply to the water heater if it is connected to a water supply with: a Chloride content > 250 mg/L; or a pH < 6; or is scaling with a Saturation Index > +0.4; or is corrosive with a Saturation Index < -1.0.

† Warranty Details: 5/3/2 warranty; 5-year cylinder supply, 3-year labour on the cylinder, 2-year parts including labour: applies to a single family domestic dwelling only. Without limiting these periods, a 5-year whole-of-product warranty applies where a rebate has been received under Solar Victoria’s Solar Homes Program for installations from 1st July 2023. All other applications have a 3/1/1 warranty; 3-year cylinder supply, 1-year cylinder labour, 1-year parts including labour.

Solahart Atmos Heat Pump Specifications

MODEL Solahart Atmos
Product Code 325HAV
Suitable for # of People (warm climate) 2 - 5
Height (A) 1631 mm
Width (B) 888 mm
Depth (C) 638 mm
Module Height (D) 1018 mm
Empty (Cartoned) 130 kg
Full 455 kg
Storage Capacity  325 lt
Power Input 800 W
Refrigerant  R134a
Element Sizes 3.6 kW
Boost Capacity 180 litres
Water Connections & Settings  
Inlet  Rp 3/4
Outlet  Rp 3/4
Tank Relief Valve Setting 1000 kPa
ECV Setting 850 kPa
Maximum Mains Pressure Settings  
With ECV 680 kPa
Without ECV 800 kPa
Min. Water Supply Pressure

200 kPa

How Heat Pump Water Heaters Work

Solahart Atmos Heat Pump Water Heater delivers hot water by efficiently utilising a free and abundant source of energy - the heat that is locked in the air around us. Even on a relatively cold day, the air has some heat which is available to be transferred to a fluid. The secret is to make the fluid even colder than the air. You can see in the diagram at step 1, that liquid refrigerant begins at high pressure before being forced through an expansion valve (2). This sudden release of pressure cools the liquid to allow it to absorb heat from the surrounding air. This valve is designed to carefully regulate how much refrigerant passes through it.

On cold days, less refrigerant passes through; the smaller amount of fluid expands faster into the available space and cools to a lower temperature. On warmer days, more refrigerant is allowed to pass through - it doesn't need to cool down as much because the air has more available heat to transfer. As the cooled refrigerant passes up the coiled tubes, air is blown over the tubes to warm the refrigerant till it becomes a vapour (3). To make the heat pump more efficient, part of the air is actually drawn from around the motor. This helps cool the motor as well as reclaiming potentially wasted heat.

Next, the low pressure vapour needs to be compressed again to return it to its original pressure (4). The temperature has by now reached around 80ºC. From here the refrigerant is pumped to the heat exchanger where it passes down a series of narrow tubes (5). The cold water is pumped up an alternating set of tubes to allow it to absorb the heat. Each time water passes through the heat exchanger it emerges around 10-15ºC hotter. When all the water in the attached storage tank reaches its pre-set temperature, the heat pump switches itself off. 

Electric Boosting

Ice may begin to form on the evaporator reducing the heat pump efficiency, when the ambient air temperature falls below 7°C and the heat pump has been operating for an extended period. At ambient air temperatures below 3°C to 5°C, the water heater deactivates the heat pump operation and switches to the booster heating unit. During this period the evaporator will defrost if necessary.

At ambient air temperatures above 45°C to 55°C, the water heater deactivates the heat pump operation and switches to the booster heating unit. The water inside the tank will be heated to a temperature of 70°C by the electric booster heating unit if heating is required. The temperature setting of the thermostat controlling the booster heating unit is not adjustable and is set at 70°C.

Freeze Protection

The water heater has a freeze protection system. The freeze protection system will protect the water heater from damage, by preventing ice forming in the waterways of the water heater, in the event of freezing conditions occurring.

If the ambient air temperature falls below 1°C and the heat pump is not operating, the system will operate the circulator periodically. During this freeze protection cycle, the circulator will operate for thirty (30) seconds and then rest for fifteen (15) minutes, before the cycle is recommenced. Water is circulated from the storage tank through the heat pump circuit, to prevent freezing in the connecting pipe work and heat pump module. The green LED will flash a series of four (4) flashes whilst the circulator is operating.




Why Solahart Solar Hot Water Systems: Download

Solahart Atmos Heat Pump Water Heater Datasheet: Download

Link to "How it Works" Video Here

Installation Manual

Solahart Atmos Heat Pump Water Heater Owner's Guide and Installation Manual: Download

Solar Incentive Forms

Small-scale Technology Certificate Assignment Form: Download