Compare Solar Quotes: the Questions That Vet the Installer, Not Just the Price

It is a Saturday morning, and two solar quotes are spread across the kitchen table. Both are headed ‘6.6 kW system’. Both are for the same roof in the same suburb, and one costs thousands of dollars more than the other. The kettle has gone cold twice while you tried to work out why.

That scene is not unusual. It is the moment most households reach a few weeks after the first ‘should we go solar?’ conversation, and it is where a good decision can quietly go off the rails. Not because solar is complicated, but because two quotes for the same roof are often not quoting the same thing at all.

A quick note before the useful part. This is general information, not personal advice. Rebate rules, prices and installer offers all move, so treat every figure here as an example and confirm the details with your installers and your state scheme before you rely on them.

Why two quotes for the same roof look so different

Solar quotes are hard to compare because they are not really prices for a single box. Each one is a bundle of separate decisions wearing one dollar figure.

The size differs: how many kilowatts of panels, what capacity of inverter, and whether a battery is part of the price or a tempting extra. The components differ, because panels and inverters come in brands and tiers, and the gap between an entry level panel and a premium one is real. The warranty differs too, both on the hardware and on the workmanship. And the price can be quoted before the rebate or after it, which changes the number on the page without changing the system.

None of that makes the job hopeless. It means the headline total is the least useful number on the page. Comparing totals before you have made the quotes describe the same thing is comparing apples with oranges, and it is exactly what the lead generation websites want you to do, because it keeps the decision on price.

There is an honest middle worth naming. Some of the spread between quotes is genuine difference in components and coverage. Some of it is margin. And a small part of the higher priced end leans on fear, the ‘do not let the cheap ones burn your house down’ school of selling. The job is to tell those apart, and you can, with a method and a set of questions.

Compare cost per kilowatt, not the total

The first rule of a fair comparison is to put every quote on the same footing before you look at money. Check three things: the size of the system in kilowatts, the components named, and whether a battery is in the price. A quote for a 6.6 kW system and a quote for a 10 kW system are not competitors. They are different sized systems, and no total-price comparison will make them fair.

Then convert each quote to a price per kilowatt. Work out the full capacity first: the panel array plus the inverter, both in kilowatts. A 6.6 kW array on a 5 kW inverter has 11.6 kW of combined capacity to divide by, and that combined figure is the fair denominator because it catches the panels and the inverter in the same sum. Divide the total installed price by that combined capacity. The number you get, dollars per kilowatt, is the figure to set side by side, because it lets a smaller system and a larger system be compared on the same scale.

Here is the arithmetic with made up, rounded numbers, because the point is the method, not the figures. Say Quote A prices a 6.6 kW array with a 5 kW inverter, 11.6 kW of combined capacity, at $9,000. That is about $776 per kilowatt. Quote B prices the same sized system, same roof, at $11,500, which is about $991 per kilowatt. On the surface the gap is $2,500. Per kilowatt of capacity it is about $215, and that is the number that tells you what the dearer quote is actually asking for each unit.

The same logic covers a battery. If a quote includes storage, keep the battery out of the solar sum: compare the solar part per kilowatt, and price the battery separately as dollars per kilowatt-hour of storage. A battery is priced against how much it can hold, not how much power it can make, so mixing it into the headline hides the one figure you need for a fair comparison. A quote that bundles a 10 kWh battery into the total without saying what the battery costs is hiding exactly that.

What a proper solar quote must itemise

A quote that is easy to compare fairly is a quote that names its parts. Work through this list and you will know whether you are looking at two versions of the same system or two different products.

• The exact number of panels, with their brand and model, not ‘premium panels’
• The inverter brand and model, and whether it is a string inverter or microinverters
• The mounting system, and whether the price covers a switchboard upgrade
• Any roof work, and what happens if the installer finds a problem once they are up there
• The warranty terms on each component and on the workmanship, in writing
• The price before the rebate and the price after it, so you know which number you are comparing

A vague quote is usually a lump sum with no detail behind it. It says ‘premium panels’ without naming a brand, gives no inverter model, and has nothing to say about what happens if your switchboard is not up to the job. Vagueness is not always a scam, but it is always a reason to ask for more before you treat the number as comparable to a detailed quote.

Vet the installer before you weigh the price

This article promised something the lead generation websites do not: that the questions that matter most are about the installer, not the number. Here is that question set.

• Is the installer an approved retailer under the Clean Energy Council scheme, or the equivalent accreditation for your state? Ask, then confirm on the public register rather than taking the logo on the quote as proof
• How long has the company actually been installing solar, not just selling it?
• Who does the work on the day? Employees of the company, or subcontractors brought in for the job?
• What is the workmanship warranty, in writing, and who stands behind it?
• What does support look like in a few years if the system underperforms and the manufacturer has restructured?

The warranty point is where an Australian discussion thread put it better than any brochure. The installer who has been around for a decade and offers their own ten year warranty, without leaning on the manufacturer, is worth more than the cheapest quote. That is the pattern worth paying for. And an installer who is hard to reach before they have your money will not get easier to reach after they have it.

Read reviews for patterns rather than single stories. Five reviews mentioning the same problem are a pattern. One angry review is often just one angry afternoon. Then ask every installer you shortlist the same questions, in the same order, and write the answers down. Answers you can compare are the only ones that help.

The rebate and the fine print

Part of the price spread comes from the rebate, and it helps to understand why. Most Australian households installing solar claim a rebate through the small-scale technology certificate scheme, usually shortened to STCs. The value of the certificates is roughly tied to the size of the system, and it can be passed through in the quoted price or claimed separately. Because it is a fixed amount per unit of capacity rather than a percentage of what you pay, it does not shrink the gap between a cheap quote and a dear one. It sits underneath both.

That is one reason the same sized system can land at very different prices, and it is why the first question to ask is whether the number on the page is before or after the rebate. Compare every quote on the same basis. If one is ‘after rebate’ and another is ‘before rebate’, put them on the same side of the line before you do the per kilowatt sum.

A worked comparison, start to finish

Now run the whole method through one realistic example, with the figures rounded to show the shape. Quote A comes in at $9,000 for a 6.6 kW system with a 5 kW inverter, entry level panels, a five year workmanship warranty and an installer who has been on the tools for two years. Quote B comes in at $11,500 for the same sized system, a named premium panel, a ten year workmanship warranty and an installer with a decade of history.

For each quote the combined panel and inverter capacity is 11.6 kW. Quote A works out at about $776 per kilowatt, and Quote B at about $991 per kilowatt. So Quote B is asking about $215 more for each kilowatt of capacity.

The question the method leaves you with is not which is cheaper, because Quote A is cheaper. It is whether the premium panel, the decade of experience and the longer warranty are worth that per unit difference to you. For some households they clearly are. For others the honest answer is that the cheaper system, properly installed, would have done the job.

Cheaper per kilowatt is not automatically better, and it is not automatically worse. It is a fact about the quote, not a verdict on the installer. The decision is the whole picture, and the table above lays it out at a glance.

The quote is the start, not the answer

So here is where it all lands. Compare solar quotes by cost per kilowatt, not by the total, after you have made them describe the same system. Read what each quote itemises, and treat vagueness as a request for more detail. Vet the installer with the same questions asked of everyone, and let the answers do the talking. And remember that a quote that will not itemise its parts is answering you, even before you have asked.

The last step is a plain one. Shortlist three installers, ask each of them the questions in this article, and lay the answers out on the same page. The right system for your roof will announce itself, and it will usually come with an installer you trust rather than the smallest number on the table.

Sources: Solar Victoria, what to look for in a solar quote · Clean Energy Council, choosing a solar installer and the approved retailer check · Australian Government, solar panels and batteries (rebate and installer guidance)