It sometimes begins with a flicker but then there’s complete silence. The quiet hum of the refrigerator dies, the lights go drab, and your laptop screen goes black in […]
What Is a Solar Hot Water System?
Solar hot water is a system that harnesses the sun’s energy to warm water for domestic use.
It’s a rational, eco-friendly solution that can significantly reduce your domestic energy bills and your carbon footprint.
Given the amount of sunshine Australia receives, it’s little wonder that solar hot water systems are so well-liked throughout the country.
But choosing the right system doesn’t always take a straightforward approach. The best solar hot water system for your household could be completely unacceptable for another.
The climate of the area you live in, the style and layout of your roof, the number of occupants in your home, and your budget will all influence your decision.
This guide will walk you through the most common types of solar hot water systems available in Australia and help you to find the best one for your situation.
Why Compare Systems Before Buying?
A solar hot water system isn’t merely another appliance—it’s an investment in your home and your ecological footprint. Although these systems may cost more to purchase upfront than standard electric or gas water heaters, the long-term savings can be considerable.
But not all systems are the same. They vary in efficiency, lifespan, installation needs, and their ability to deal with varying weather patterns.
For instance, a unit that performs well in sunny Perth may not perform equally well in Tasmania’s cloudier, cooler regions.
Similarly, if your roof cannot carry heavy loads, some possibilities will be ruled out. Browsing systems initially will prevent you from spending more money than you like on unnecessary features or having a poor-performing unit for your region.
It’s a matter of making an informed choice today and also down the road.
Types of Solar Hot Water Systems
Australia’s climatic variability suggests that selecting the most suitable solar hot water system is critical to efficiency and affordability.
The four primary types are outlined below, each with its strengths and optimal use.
Flat Plate Collectors
Flat plate collectors are one of the most common and low-cost solar water heating systems. They are flat metal absorber plates housed inside an insulated box and covered with a plastic or glass panel.
Either water or a heat transfer fluid is pumped through pipes in the back of the plate, absorbing the sun’s heat and transferring it to your storage tank.
Climate Suitability
The systems perform optimally in temperate and warm weather conditions where sunlight is consistent.
In frost-prone areas and cold regions, performance decreases significantly unless they are equipped with freeze protection.
System Efficiency
The systems are moderately efficient.
Flat plate collectors typically come with certified performance ratings like SRCC OG-300.
They perform optimally under direct sunlight but are more prone to losing heat compared to evacuated tubes.
Installation Complexity
These are roof-mounted and usually part of thermosiphon packages, so the tank also sits on the roof. That adds extra weight and structure requirements. Space requires a considerable surface area to be exposed to the sun for optimal operation.
Cost Comparison
- Tips Cost: Typically, the lowest of any of the solar systems.
- Maintenance: Low; only occasional checks for leaks, insulation, or glazing.
- Payback Period: Faster return on investment in sunny areas due to reduced initial cost.
Lifespan and Durability
Most flat plate systems last 10–15 years.
Over time, the absorber plate may corrode, and the insulation may wear away. Nevertheless, components are affordably priced and easy to replace.
Advantages
These systems are simple to plan, cost less to install, and work well in hot and sunny places. They are low-maintenance and can last for many years with proper care.
Disadvantages
Flat plate collectors are not as efficient in cold climates or on cloudy days since they are exposed to colder outside air temperatures. They’re also not as good at gathering low-angle sun during winter months.
These Panels are Best for:
Homes in warm, sunny climates like Brisbane, Perth, or Adelaide. It is ideal for budget-minded households looking for high reliability in mild climates.
Evacuated Tube Collectors
Evacuated tube collectors are another upscale solar hot water option.
Each tube has two layers of glass with a vacuum between them, containing a metal heat pipe. This setup enormously reduces heat loss, even on cloudy or cold days.
Climate Suitability
Suitable for cold, alpine, or cloudy locations.
The vacuum space between glass tubes reduces heat loss, and most systems contain integral freeze protection mechanisms.
System Efficiency
Evacuated tube systems are amongst the highest-efficiency systems available.
That they can absorb solar radiation from all angles of the sun results in them functioning even under overcast skies or in winter.
Certified performance ratings consistently receive outstanding ratings.
Installation Complexity
These are used in both split and thermosiphon systems.
They weigh less per panel than flat plates but occupy a bit of extra space because tubes are spaced apart. Tubes are breakable, so they require more careful handling during installation.
Cost Compare
The installation/ Initial Cost is more than flat plates
Calls for, on occasion, replacement of individual tubes, though they can break easily. Pump systems need servicing, particularly in split setups.
The Payback Period is moderate. More expense is balanced by increased efficiency in poor weather zones.
Lifespan and Durability
Evoluted tubes have a lifespan of 15–20 years with proper maintenance. There can be a failure from vacuum or cracked tubes after years, but replacing individual tubes is not very costly.
Advantages
These systems are highly efficient for cold or changeable climates.
The vacuum insulation ensures that they retain heat even on chilly mornings or cloudy days.
They also have the advantage of their cylindrical shape, as they can absorb sunlight from any direction during the day, which maximises their performance.
Disadvantages
Evacuated tube systems cost more to purchase and install. Individual tubes are also more likely to break and will be expensive to replace if they do fail.
These Types Are Best For
Lower-temperature applications, such as those in Melbourne, Hobart, or the Blue Mountains. It is ideal for residences that are willing to pay extra upfront for high year-round performance.
Thermosiphon Systems
Thermosiphon systems incorporate the solar collector and the storage tank in one single unit that is mounted on the roof.
The system utilises natural convection: as sunlight heats the water in the collector, it naturally circulates into the tank without the need for a pump.
System Efficiency
Efficiencies are moderate and are a function of the collector utilised. Ms
With no pumps needed for circulation, energy loss in this manner is nonexistent.
However, radiation heat loss from the roof-mounted storage tank will slightly lower efficiency overall.
Installation Complexity
Structurally more demanding — the roof will need to be capable of supporting a full storage tank (typically 200–400 kg in total). Space must also be available for the entire unit. Appearance can be an issue for some owners.
Cost Comparison
- The initial Cost is mid-range.
- Maintenance is very low. No moving parts = fewer things to fail.
- Payback Period is short to medium and very cost-effective in the right climate.
Lifespan and Durability
These units are 10–15 years of low maintenance.
The largest risk is the exterior exposure of the tank, which may deteriorate more rapidly as a result of weather or UV damage.
Advantages
Being less complex with no electrical pumping to provide for, thermosiphon systems are cost-efficient and have fewer parts that may require maintenance.
This keeps the maintenance cost low.
Disadvantages
The roof must be strong enough to support the big storage tank, especially when full.
Some homeowners also find the tank mounted on the roof to be aesthetically displeasing.
Also, since the tank is open, heat loss occurs quickly in cold climates.
Homes in consistently sunny areas like Darwin, Townsville, or Alice Springs.
It is best suited for homeowners who prioritise low-maintenance, energy-efficient means and don’t care about roof appearance or carrying capacity.
Split Systems (Pump Circulated)
Split systems divide the solar collector (which stays on the roof) and storage tank (which is at ground level or inside the home). There is a low-power, low-energy pump operating between the two units, circulating water or heat-transfer fluid.
Climate Suitability
Extremely adaptable. Works in any climate if a proper collector (flat plate or evacuated tube) is used. Freeze protection is easier to integrate with the controller and pump set.
System Efficiency
Efficiency will be a function of the collector used in combination with the system. Fluid circulating pumps reduce pipework heat losses and allow better tank insulation in the ground.
Installation Complexity
The system is more complicated compared to the thermosiphon types.
It involves installing pipes from the roof to the floor and adding the electric pump mechanism.
But the system doesn’t press the roof under the heavy tanks; it’s highly appropriate for constructions where structural or aesthetic limitations are present.
Cost Comparison
Pump controller maintenance should be performed periodically.
The Payback Period is longer than typical, though efficiency and style can justify the investment in luxury homes.
Lifespan and Durability
The systems last 15–20 years well installed. Pumps have to be replaced after 7–10 years. As the tank is ground-mounted, it’s frequently better weather-protected and lasts longer.
Advantages
These systems are more flexible in design and are ideal where there is limited space on the roof or where it is weak to carry a heavy tank.
The ground-mounted tank is also larger and better insulated, and energy can be stored more efficiently.
Split systems can work with either flat plate or evacuated tube collectors, and one may be designed according to climate and affordability.
Disadvantages
The system’s complexity results in additional components requiring servicing over the long term. More expensive to install than basic thermosiphon or flat plate systems as well.
These Systems are Best for
Designer homes, those with architectural or structural roof restrictions, or sites where local council provisions restrict exposed rooftop installations.
Common on city lots like inner Sydney or Melbourne suburbs.
Best Solar Hot Water System for Various Needs
Best for Cold Climates: Evacuated tube systems—they keep the heat on even in freezing temperatures.
Best for Budget Buyers: Flat plate systems—steady and cost-effective for sunny climates.
Best for Large Families: Large storage split systems—provide improved heat storage and water volume control.
Comparison Table
| System Type | Efficiency | Cost Range (AUD) | Climate Suitability | Lifespan | Maintenance |
| Flat Plate | Moderate | $3,000–$5,000 | Warm to temperate | 15–20 years | Low to medium |
| Evacuated Tube | High | $4,000–$7,000 | Cold or variable | 15–25 years | Medium |
| Thermosiphon | Moderate | $3,000–$6,000 | Warm and sunny | 10–15 years | Low |
| Split System | High | $4,500–$8,000 | All climates (flexible) | 15–20 years | Medium to high |
Choosing the Best Solar Hot Water System for Your Needs
Best suited for Cold Climates:
Evacuated tube systems work best where there are long winters, frosts, or lots of cloudy days.
They enjoy the optimal insulation and heat retention characteristics that suit Canberra, Hobart, and the Victorian Alps.
Best for Budget Buyers:
Flat plate systems are inexpensive to install and maintain, and deliver good hot water in sunny locations without breaking the bank.
Priced right for homes in Queensland or Western Australia.
Best for Large Families:
Large storage tank split systems offer plenty of hot water on tap, even at peak usage during the morning or evening.
Their configurable nature allows for a higher capacity of water and energy storage.
Best for Aesthetic or Design-Conscious Homes:
Split systems win this point as well by allowing the storage tank to be placed out of sight and leaving less visual clutter on architect-designed or heritage-listed buildings.
Government Rebates & Incentives
Australians can benefit from a number of state and federal rebates to cover installation expenses.
The Small-scale Renewable Energy Scheme (SRES) provides Small-scale Technology Certificates (STCs), which can lower the initial cost based on your location and system size.
There are also extra incentives available in some states:
- Victoria: Rebates of up to $1,000 through the Solar Homes Program
- New South Wales: Low-interest loans and rebate incentives
- Queensland: Occasional solar bonus schemes and local council rebates
- ACT & Tasmania: Energy efficiency upgrades with targeted incentives
Visit your local government website or consult with an accredited installer to determine your eligibility.
Frequently Asked Questions
How much will I save with a solar hot water system?
You may be able to save 60–80% of your hot water energy costs, depending on usage and system performance.
Do I need a backup system?
Yes. Most are equipped with electric or gas boosters for days when it’s cloudy or heavy use.
How long do the systems last?
Most systems last between 15 and 25 years if maintained properly.
Is it worth putting in cloudy or cold locations?
Yes. Evacuated tube and split systems both work well under these conditions—just make sure you use the proper type.
