How does our solar-sharing technology, SolShare, compare in terms of cost against individual solar systems for apartments, units and townhouses?
In this article, we assess this by breaking down costs, lifetime savings and payback periods to determine the ROI of each option.
Australians have some of the highest rates of residential rooftop solar in the world - around 33%!
Around 16% of Australians are now living in apartments but, until recently, there was no feasible way for them to get rooftop solar.
That's why Allume invented SolShare - this world-first, Australian-made technology divides the electricity from a single rooftop solar system and shares it fairly between apartments each month.
This overcomes many of the technical, legal and financial barriers to solar for strata and there are now over 3,000 apartments connected to clean, affordable energy from their rooftops, thanks to SolShare.
The only alternative to SolShare is to allocate each apartment an equal space on the roof and to install individual solar systems.
But for the vast majority of apartments in Australia, SolShare will deliver better return on investment - see costing below!
Firstly, let's look at what impacts the lifetime cost of a solar system.
Apartment blocks only have so much roof space available and this impacts how many solar panels can fit onto the roof.
Average allocations of 1 – 2kW per apartment are typical. As you increase the amount of solar per tenancy, it has diminishing returns (it’s not a linear increase). For example, increasing allocation from 1-1.5kW will provide a larger benefit than an increase from 1.5-2.0kW.
One of the main benefits of SolShare versus individual systems is that it maximises the amount of solar consumed (more info below). This essentially means higher bill savings (because the energy you feed back into the grid is worth a lot less than the energy you have to buy from your retailer).
Installation costs vary widely depending on the height of the building, roof pitch, roof access, switchboard upgrade requirements and much more. An installer will always do an in-person site inspection before the final quote to determine these factors.
Some of these costs are simplified with SolShare, such as wiring and racking; but more importantly, SolShare also shares inverters (and batteries if relevant), which add to equipment costs.
Additional maintenance costs affect the overall return on investment of the solar system across its lifetime:
The costs above must be paid per apartment with individual solar systems, versus once with SolShare.
Additionally, multiple individually owned systems on a commonly owned roof lead to complexities in ownership, e.g. one owner has their system serviced by an installer and they damage the roof - where does the liability lie?
With SolShare, the responsibility lies with owners corporation.
*Noting that due to Victoria’s backstop mechanism, an internet connection is required to allow any exported solar credits to be obtained by the apartment
Is the building fully electrified or does it use gas too? Fully electrified apartments will see higher bill savings because electric appliances that replace gas - heating, hot water, stovetops and ovens are high-energy users.
If the building isn't electrified, will it be soon? Will electric vehicle charging be added at any stage? If so, it's safe to assume higher energy bills when doing calculations.
The age and efficiency of the appliances within each apartment will also play an impact. Upgrading to smart appliances can hugely improve solar utilisation - see more tips below!
It's important to consider the behaviour of the typical apartment household in question. For example, do people work from home, do they work part-time, are they retired, do they have children?
Behaviour and preferences impact the times of day we use energy, which is really important in understanding how much solar we'll consume and whether batteries might improve payback periods.
We’ve found through experience, the average electricity consumption of an apartment in Australia is approximately 14kWh per day, so you can use this if you don't have energy bills from residents.
Once solar is installed, residents may be able to move some heavy energy loads to the daytime, timing dishwasher cycles or pre-cooling the space during summer.
It is common practice to include an increase in electricity prices per annum in calculations. A 4-6% increase in the year-on-year cost of electricity is a safe assumption, as this mirrors likely inflation.
Many government solar-for-apartment grants and rebates require payback periods specified. Ensure this is considered when sizing systems and assessing project feasibility.
A solar system's 'self-consumption' or 'self-utilisation' rate is instrumental to calculating return on investment because it impacts bill savings significantly.
Self-consumption relates to the percentage of solar that's used by residents, versus what is sent back to the grid.
You pay your retailer a lot more to buy energy from them than they will pay you for selling it back, so the higher the self-consumption rate, the better.
According to Griffith University, a generous estimation of the average annual rate of self-consumption is 36%. That's best case scenario, and typically requires behaviour change from residents.
A SolShare solar system has, on average, 50% greater self-consumption rate by comparison with individual solar systems, including microinverters.
Below is the average self-consumption range for a SolShare solar system by system size:
|
Partially Electrified |
1-1.25kW |
1.25-1.5KW |
1.5kW-1.75kW |
1.75-2.0kW |
|---|---|---|---|---|
|
Partially Electrified |
40 - 70% |
30 - 65% |
25 - 60% |
25 - 60% |
|
Fully Electrified |
45 - 75% |
40 - 70% |
35 - 65% |
35 - 65% |
To illustrate this using a real-life example, below is a screenshot from our energy monitoring portal, SolCentre, of a SolShare apartment block in New South Wales over 1 year (from November 2023 to October 2024 inclusive):
As you can see, the utilisation rate (solar consumed divided by solar delivered) is roughly 56%, much higher than it would have been with individual systems.
With traditional solar systems (without a battery), you are only consuming solar when your household is using electrical appliances during daylight hours. The rest gets fed back into the grid, usually for a very low price - around 6c / kWh, compared with ~30c / kWh to buy energy from your retailer.
Apartment buildings with individual solar systems can only access the 2-3 panels of solar that they are connected to, unlike SolShare, where 15+ panels can be accessed at any time by a single apartment.
SolShare has more households to feed energy into at any one time, so much more of the energy it produces can be used compared with individual systems. Its algorithm ensures everyone gets the same amount throughout the month.
For townhouses or blocks of five units or less, individual systems may work out better financially but for the vast majority of apartments in Australia, shared solar provides a much more favourable return on investment.
Interested in shared solar for your apartment? Get started below!
Use our shared-solar calculator tool to get a rough idea of the cost of solar for your apartment or enquire below to receive a desktop assessment of your apartment block.
We'll lay out the upfront cost (with and without rebates), monthly savings per apartment and payback period!