Why the cheapest solar quote almost always costs the most.

Every week we sit with someone who chose the cheapest quote three years ago and is now paying twice. They didn't get a bargain. They got a head start on a second install.

Solar is the only ~$15,000 purchase most Australians make where the upfront number is treated like the only number. Cars get test driven. Houses get inspected. Solar gets quoted, ranked by sticker price, and signed in a kitchen on a Tuesday night. Here's how that maths actually works over the life of the system — and why "cheapest" is the most expensive label in the industry.

01The headline number is the smallest part of the cost

When a salesperson quotes you $8,990 for a 6.6kW system, they're quoting one slice of a ten-to-twenty-year cost. The honest way to think about a solar install is total cost of ownership, not sticker price. The components of that lifetime cost look roughly like this:

• Upfront install — panels, inverter, racking, labour, paperwork. This is the only number on the quote.
• Inverter replacement — most budget string inverters survive 8–10 years; premium ones get to 12–15. A replacement is $1,800 to $3,500 fitted.
• Panel degradation — quality panels lose ~0.4% output per year. Cheap panels lose 1–2%. Over 15 years that's the difference between a system still doing 88% of nameplate vs. one doing 65%.
• Warranty claims that go nowhere — if your retailer is gone in three years (and a third of Australian solar retailers are), the manufacturer warranty is technically valid but the installer warranty is worthless and the labour to swap a panel is on you.
• Under-sizing — a system that's 2kW too small for your usage gives you 8 years of higher-than-necessary bills. We've costed this many times: it's usually $4,000–$7,000 across the system's life.

The headline price usually represents 55–65% of the real lifetime cost. The other 35–45% is decided by the brands, the installer, and the sizing — exactly the parts the cheapest quote tends to get wrong.

02What "cheapest" usually means under the hood

The retailer offering the sharpest sticker price is, almost without exception, doing one or more of the following:

1. Selling you a smaller system than your bill warrants. 6.6kW is the magic marketing number because it fits inside the standard 5kW single-phase inverter and lets retailers advertise an entry-level price. For most Australian households with electric hot water, ducted aircon, or an EV, 6.6kW is two-thirds of what you actually need.
2. Pairing tier-one panels with a budget inverter — Trina, Jinko, LONGi panels with a no-name Chinese inverter that has limited Australian service infrastructure. The panels you'll see for 20+ years; the inverter you'll see fail at year 7 with a six-week wait for a replacement.
3. Quoting on hardware they've already bought, not hardware that suits you. Warehouses have stock to clear. The sharpest price in the market this week is whatever the salesperson's boss is trying to move.
4. Cutting labour to the bone. One-day installs by a CEC-accredited person + two apprentices who haven't yet finished their tickets. Most of the install issues we see — DC isolators that fail their first inspection, rails that aren't level, conduits run on the surface of the roof — come from this combination.
5. Pricing the warranty out of the deal entirely. The CEC mandates a 5-year workmanship warranty, but it's only worth anything if the company answers the phone. Many budget retailers won't.

None of these things are visible on a quote PDF. All of them show up in years 4 through 10, when the salesperson is selling someone else's system in a different suburb.

03A worked example: $9k vs $13.5k over seven years

Here's a real comparison from a recent customer in western Sydney. Same roof, same household, two quotes.

The "cheap" install ended up $1,900 more expensive over seven years — and that's before you count the fact that the right-sized system is offsetting a meaningfully larger chunk of the household's bill every quarter. Add the bill differential and the cheap install is $4,500 behind at the seven-year mark and falling further every year.

This is not an unusual outcome. It's the average outcome when "cheapest" is the deciding factor.

04The two-install problem

The most expensive thing that can happen to a solar owner is to buy the wrong system, regret it, and buy a second one. We see this all the time. The first install is undersized or has hardware that flakes out by year six; the homeowner is now five-plus years older, electricity rates have moved, and they end up commissioning a near-complete replacement at full price.

Two systems over twelve years where one good one would have done the whole job. The "cheap" first install ends up costing roughly 1.5 to 1.8x what a properly sized install would have, once you count the wasted upfront, the bills paid during the half-working years, and the second install. The kicker: the panels from the first system frequently can't be re-used because newer inverters don't string well with older modules.

05How to spot a false-economy quote in 30 seconds

You don't need to be a solar engineer to see most of these. Read the quote, look for these signs:

1. The system size is exactly 6.6kW when your quarterly bill is $700+ and you have ducted aircon. That's a sticker-price-driven number, not a usage-driven one.
2. The inverter is unfamiliar. Sungrow, Fronius, SMA, SolarEdge, Enphase — these are the names you want. Anything else, ask a consultant to look it up.
3. The warranty section is shorter than half a page. A real warranty disclosure runs to a couple of pages because it has to specify product, performance, and workmanship terms separately.
4. The installer is a different company from the retailer and you can't find them on the CEC installer database under their own name. That means the install is being sub-contracted to whoever has capacity that week.
5. The quote can't be paused. If the price expires at the end of the meeting, the price is fictional. A real quote holds for 14 days minimum.

06The honest summary

Cheap quotes exist because cheap quotes work — they convert, they hit retailer revenue targets, and the customer doesn't realise what happened until five years later. The retailer was paid in week one. You're paying for the next twenty.

The solar industry doesn't fail because the technology is bad. Panels are extraordinary now. The technology is fine. What fails is the buying process — when "cheapest" is the input, "regret" is the output.

The fix is not to spend more for the sake of it. The fix is to pay for the right system, sized to your actual usage, with hardware brands that have Australian service infrastructure, installed by a team that does its own labour. That number is sometimes the second-cheapest quote on your table. It is almost never the cheapest. And it's the only one that's still earning you money in year fifteen.

Talk to a consultant before you sign anything. You only buy solar once if you buy it right.