Two quotes for the same roof can land 3kW apart, and the gap is almost always in how the system was sized, not the panels themselves. Here's what that gap actually looks like in practice.
The Usual Approach
Generic solar quote
A standard 6.6kW system gets quoted regardless of your roof, your usage or your bill, because it's the size most installers keep in stock. Result: undersized for anyone paying more than $700 a quarter.
Comparison site estimate
No site visit, no roof assessment, no look at your actual bills. The number you see is built to win the click, not to match your property — and no installer is accountable once the sale is made.
The SEG Approach
Based on your last 12 months of bills
We review your actual usage, assess your roof in person, and design a system around your household, not a template — a real payback period, installed by the crew who designed it.
The full process runs five stages. Here's where solar sizing fits into the first three.
We review your last 12 months of bills, assess your roof, and map your usage before recommending a system size.
Your system is specified from the audit data, not a catalogue size. You get an exact payback period and 25-year return before you sign anything.
STC certificates and any applicable battery rebates are calculated and applied as an upfront discount, handled entirely by us.
The panels rarely fail. What tends to go wrong is everything around them.
Deducted from the price you're quoted, not promised as a future refund you have to chase.
You're told exactly which panels, inverter and hardware are going on your roof.
Backed in writing, not a handshake. If it's our fault in year 12, it's still our problem.
A 6.6kW system and a 10kW system can cost a similar amount once STC rebates are applied, but they solve very different problems. A household running a pool and ducted air conditioning through summer needs meaningfully more capacity than one that doesn't, and quoting the smaller system anyway is one of the most common reasons homeowners feel let down by solar a year or two after install. Our free audit exists specifically to avoid that outcome.
Small-scale Technology Certificates are created based on your system's size, your location and the number of years remaining in the scheme, then assigned to us as an upfront discount on your quote rather than something you claim yourself after the fact. The exact figure depends on current certificate pricing at the time of your install, which is why we calculate it during your audit rather than advertising a flat number that may not hold by the time you sign.
In practice, this means we look at your last 12 months of bills, not just your most recent one, to account for seasonal swings. We assess your roof's orientation, pitch and any shading from trees or neighbouring structures. Ducted air conditioning, pool pumps, electric vehicles and any planned additions like a home battery are all factored into the design before a number gets quoted.
Solar alone still leaves you buying power back from the grid every evening, often at several times the rate you were paid for exporting it during the day. Most of our residential solar customers eventually add a battery, either at the same time as the solar install or once the panels have paid down enough of the system cost to justify it.
Your 25-year workmanship warranty and the manufacturer warranties on your panels and inverter don't end when the installers leave. We monitor system performance remotely and flag any drop in output before it shows up as a jump in your next bill. If you'd like to see the full process from first contact through to year 25, our how it works page walks through every stage, or get in touch through our contact page to book your free audit.
Step 1 is a free, no-obligation energy audit. We review your actual bills and tell you exactly what’s possible — including if solar won't deliver the return you need. We'll contact you within 1 business day.
Book Your Free Energy Audit