For years, there was a simple rule most Aussies were told when getting solar.
“Look at your last 12 months of power bills. Size a system to match that usage. Let the excess go back to the grid. Enjoy the savings.”
And for a long time, that advice worked.
Back then, most homes had fairly predictable electricity patterns. Gas often handled hot water and heating. Feed-in tariffs (FiTs) were still worthwhile. Batteries were rare.
Solar’s job was straightforward: reduce the power bill by exporting what you didn’t use.
However, things are changing faster than that advice.
Electric Vehicles (EVs) are arriving in driveways. Heat pump hot water systems are replacing gas. Reverse-cycle air conditioning is doing the work of old heaters. More people are working from home and using electricity during the day. FiTs are now at historic lows. Batteries are becoming a big part of the conversation.
In 2026, it’s no longer just to offset a bill. Now, it’s time to run an increasingly electric home from your own energy. And that means many solar systems today are still designed for how homes used to use power, not for how they are about to.
Your home is about to use far more electricity than it does today
The issue isn’t just that homes are changing. It’s that future electricity use is no longer visible in your past bills.
When installers ask for the last 12 months of usage, they’re seeing a snapshot of a home before major changes happen. That data doesn’t show planned upgrades, lifestyle shifts, or appliances you haven’t installed yet.
And this is where solar sizing quietly goes wrong.
A household planning to buy an EV in the next year. A family is considering switching to a heat pump for hot water. Someone is renovating and adding reverse-cycle air conditioning. A couple are now working from home most days. None of that appears in historical usage data.
Yet these are exactly the things that determine how much solar, and whether a battery, actually makes sense. This is why two homes with identical past bills can need completely different systems.
One is staying as it is. The other is about to become far more electric. If a system is sized to yesterday’s numbers, it will often be undersized for tomorrow’s reality.
Why many solar quotes skip the design conversation entirely
Today, many solar quotes jump straight to system size, panels, inverter, and price before anyone has asked how the home actually runs.
The conversation often sounds like this:
Roof space. System size. Budget. Done.
What’s missing is the part where someone asks how electricity moves through the house, what loads run when, what’s likely to change, and how the system will physically integrate with the switchboard, tariffs, and backup needs.
Modern quoting has become faster and more standardised, and the design step is quietly disappearing.
You can see it in the questions that aren’t asked:
- Which circuits would you want backed up in a blackout?
- Where will a battery actually go?
- Are you on a time-of-use tariff?
- Do you run heavy loads during the day or night?
- Is your switchboard even ready for what’s being proposed?
These aren’t upsell questions, but they are about design.
When these are skipped, the result is a system chosen from a catalogue rather than built around how the home works.
EVs break the old solar sizing formula completely
Nothing exposes the limits of traditional solar sizing more than an electric vehicle. An EV is not just another appliance. It’s a mobile battery that regularly needs a large amount of energy in a short window of time. And how and when that charging happens has a huge impact on how a solar system should be designed.
If the car is charged at night on off-peak rates, solar alone doesn’t solve the problem. If the car is charged during the day, the system needs to be large enough to cover both households loads and the car at the same time. If a battery is involved, it needs to be sized and configured with this in mind.
This is where copying someone else’s system quickly falls apart.
Two households with identical roofs can have completely different EV charging habits. One might trickle charge overnight. Another might top up during the day from solar. Another might rely on a battery to cover evening charging.
Each scenario needs a different approach to system size, battery choice, and tariff setup. However, if the quote never asks how the EV will be charged, the system is being designed without one of the biggest loads in the same home being considered at all.
Heat pumps and daytime loads change how solar should be used
One of the biggest shifts in modern homes is not just how much electricity is used, but when it’s used.
Heat pump hot water systems, reverse-cycle heating and cooling, pool pumps, and people working from home all create meaningful daytime demand. This is exactly when solar is producing its peak output.
In older solar thinking, excess daytime generation was expected to flow back to the grid. That was normal, and often worthwhile when FiTs were higher.
Today, the smarter outcome is different.
The goal is to use as much of that solar energy inside the home as possible. Running hot water systems, heating or cooling the house, and shifting appliance use into the middle of the day becomes part of the design thinking.
This changes how a system should be sized and how it should be configured. It’s no longer just about how many panels fit on the roof. It’s about how the home can be set up to absorb that energy when it’s available.
If this isn’t part of the conversation, the system is missing one of the easiest opportunities to improve performance and reduce reliance on the grid.
The shift from reducing bills to powering an electric home
For a long time, solar was sold on a simple promise: lower your electricity bill. That framing made sense when most major energy uses in the home still ran on gas or petrol, and when exporting excess solar to the grid was financially attractive.
Today, the role of solar is changing. As homes replace gas appliances, add EVs, and rely more on electric heating and cooling, solar is no longer just a way to trim costs. It becomes the primary source for how the household runs. This is a different goal entirely.
Instead of asking, “How much of my bill can this system offset?”, the more useful question is, “How much of my home can this system power?”
That affects decisions about system size, whether a battery makes sense, how loads are timed, and how tariffs are used. It turns solar from a bill-reduction tool into part of a broader home energy setup. If the design conversation is still centred on savings alone, it misses the bigger opportunity.
What a 2026 solar design conversation should include
By this point, the difference between a quote and a design becomes clear. A design starts with questions, not components.
Before system size, panels, pr price are discussed, a good installer should try to understand how the home works now and how it is likely to change over the next few years.
That conversation should cover things like:
- Whether an EV is planned and how it will be charged
- If gas appliances are likely to be replaced with electric alternatives
- How much time do people spend at home during the day
- Whether blackout backup is important and which circuits matter most
- What tariff does the household have and whether it suits their usage
- Whether the switchboard and layout can support what’s being proposed
None of these are sales questions. They are design questions that shape what the system should actually look like.
If these topics never come up, it’s a strong sign that the system is being selected from a package rather than built around the household.
Why two identical houses can need completely different systems
From the street, two homes can look almost the same. Same roof size. Same orientation. Similar electricity bills.
But once you look inside, the way those homes use energy can be completely different.
One household might still rely on gas for hot water and heating, be out during the day, and have no plans to change much. Another might be planning to buy an EV, install a heat pump, work from home most days, and add a battery in the future.
On paper, these homes can appear identical to an installer working only from historical usage and roof space. In reality, they need very different approaches to system size, battery planning, and how the solar will be used.
This is where catalogue-style thinking falls apart.
Solar is not being designed for the roof. It needs to be designed for the lifestyle inside the house.
Solar is now an energy system
The way Australians use electricity at home is changing faster than the way solar is often quoted.
What used to be a straightforward decision based on past bills and roof space is now tied to EV charging, heat pumps, daytime usage, tariffs, backup needs, and how the household is likely to evolve over the next few years.
This is why many people end up disappointed with systems that looked fine on paper. The equipment isn’t necessarily wrong. The system was simply never designed around how the home actually works.
Solar, batteries, appliances, vehicles, and tariffs now form one connected setup. Treating solar as a standalone product misses how these pieces interact.
If a quote focuses only on system size, panels, and price, it’s worth pausing. The most important part of the process should be the conversation that happens before any of those things are discussed.
Because in 2026, the quality of a solar system depends less on what’s on the roof and more on whether anyone took the time to design it for the home beneath it.
Energy Matters has been in the solar industry since 2005 and has helped over 40,000 Australian households in their journey to energy independence.
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