Table of Contents
- Why Solar Quote Comparison Matters More Than Ever
- What to Look For in a Solar Quote: 10 Non-Negotiables
- STC Rebate Explained: How It Changes Your Quote
- How to Tell If You’re Working With a CEC Accredited Solar Installer
- Your Solar Installation Contract Checklist
- Common Mistakes When Comparing Solar Quotes
- From Quote to Install: What Happens After You Sign
- Frequently Asked Questions
Last Updated: September 14, 2026
Why Solar Quote Comparison Matters More Than Ever
A solar quote comparison is the process of normalising multiple installation proposals onto the same measures, so price, system size, hardware and rebates can be judged side by side. Without that normalisation, the cheapest-looking quote often turns out to be the most expensive system.
At GridFree Solar, we see the same pattern repeatedly: homeowners collect three or four proposals, feel overwhelmed by the different formats, and default to the lowest headline number. That number rarely reflects the best value. The Clean Energy Regulator’s guidance on the Small-scale Renewable Energy Scheme sets out how rebates are calculated, which is why two quotes for identical hardware can differ by thousands.
Below, we break down exactly how to compare quotes line by line, what a fair contract includes, and the mistakes that cost homeowners the most.
What to Look For in a Solar Quote: 10 Non-Negotiables
A complete solar quote should state system size, panel and inverter models, total installed price, rebate treatment, warranty terms and what is excluded. If any of those are missing, the quote cannot be compared fairly against another.
Work through this checklist before you rank anything:
- System size in kilowatts peak (kWp) and estimated annual output
- Panel brand, model and wattage
- Inverter type (string, hybrid or microinverter) and efficiency rating
- Battery capacity in kWh, if included
- Total installed price, inclusive of GST
- STC rebate value and whether it is deducted upfront or claimed later
- Warranty periods for panels, inverter, battery and workmanship
- Mounting hardware and roof condition allowances
- Grid connection and meter upgrade costs
- Monitoring hardware and app access
Quotes that omit the inverter model or warranty terms are the hardest to compare and the easiest to inflate. Ask for the missing detail in writing before you shortlist anything.
Build a Quote Comparison Sheet Before You Read a Single Price
The fastest way to normalise three or four proposals is to move every figure into one spreadsheet with the same rows. Most homeowners skip this step and end up comparing a 6.6 kW string system against a 10 kW hybrid with a battery, which tells them nothing.
Set up your sheet with these column headers, one column per quote:
| Row | Quote A | Quote B | Quote C |
|---|---|---|---|
| System size (kWp) | |||
| Estimated annual output (kWh) | |||
| Panel brand, model, wattage | |||
| Inverter brand, model, type | |||
| Battery capacity (kWh) | |||
| Total price incl. GST | |||
| STC rebate treatment | |||
| Net price after rebate | |||
| Panel warranty (years) | |||
| Inverter warranty (years) | |||
| Workmanship warranty (years) | |||
| Monitoring included (Y/N) | |||
| Switchboard upgrade included (Y/N) | |||
| Scaffolding / access included (Y/N) | |||
| Estimated install window |
Once the grid is filled, sort by net price after rebate, then read across each row. The quote that looks cheapest on the headline number is frequently the one with the shortest workmanship warranty, no monitoring, and a switchboard upgrade listed as an exclusion.
Normalise the Numbers Before You Rank Them
Two adjustments make the comparison honest:
- Price per kilowatt. Divide the net price after rebate by the system size in kWp. This lets you compare a 6.6 kW and a 10 kW quote on the same basis.
- Price per estimated annual kilowatt-hour. Divide the net price by the installer’s estimated annual output figure. This is the only way to see whether a shaded north-facing system is genuinely cheaper than an unshaded one of the same size.
If an installer will not provide an estimated annual output figure in kWh, treat that as a red flag. Every credible design tool produces one.
System Size, Output and Component Quality
System size tells you capacity; system output tells you what it will actually produce. A 6.6 kW system on a shaded east-facing roof can underperform a 5 kW system on an unshaded north-facing roof. Ask each installer for the estimated annual generation figure in kWh, not just the panel count.
Component quality matters just as much. Tier 1 panels and a reputable inverter brand typically carry longer performance warranties and slower panel degradation. Cheap mounting hardware is a common failure point that no warranty covers well.
Quote Transparency and What’s Excluded
Transparency is the single best predictor of a smooth installation. A good quote lists exclusions explicitly: switchboard upgrades, asbestos removal, trenching, multi-storey access and scaffolding. Those items are the hidden costs that turn a competitive quote into an average one.
Keep a second tab in your spreadsheet for exclusions. When a quote lists an item as excluded, note the likely cost range beside it so you can see the real total before you sign.
STC Rebate Explained: How It Changes Your Quote
The STC rebate is a federal incentive under the Small-scale Renewable Energy Scheme that reduces your upfront cost based on system size, location and installation date. Installers usually deduct it from the quoted price, but the value shifts as the scheme winds down.
That is why you should never compare two quotes on the final number alone. Ask whether the rebate is deducted upfront or claimed separately, and confirm the certificate quantity in writing. For battery systems, the Cheaper Home Batteries Program applies separately, and eligibility rules are worth checking against the Department of Climate Change, Energy, the Environment and Water before you sign. Discrepancies in equipment quality and installation standards often explain why quotes vary, making it essential to evaluate the underlying technical specifications alongside your financial projections.
How to Tell If You’re Working With a CEC Accredited Solar Installer
A CEC accredited solar installer has completed Clean Energy Council training and is listed on the Council’s approved installer database. Accreditation is a prerequisite for your system to qualify for rebates, so it is not optional.
Verify accreditation directly rather than taking a logo at face value. Check the installer’s name, accreditation number and expiry date on the Clean Energy Council’s approved installer finder. Then confirm the designer and the on-site electrician are both covered, because accreditation attaches to individuals, not just companies.
Ask who will actually be on your roof. Some sales companies subcontract installation to third parties, which can complicate warranty claims if workmanship issues appear later.
Your Solar Installation Contract Checklist
A solar installation contract should lock in the system specification, price, timeline, warranty terms and dispute process. Verbal promises about future performance are worth nothing once the deposit clears.
Before signing, confirm the contract includes:
- Exact panel, inverter and battery model numbers
- Total installed price with GST and rebate treatment itemised
- Estimated commissioning date and weather delay provisions
- Workmanship warranty length and what it covers
- Compliance statement referencing AS/NZS 5033 and AS/NZS 5139 where a battery is included
- Certificate of Electrical Safety provision on completion
- Cooling-off period and deposit terms
If any of those are absent, request an amended contract. A reputable installer will provide it without argument.
Common Mistakes When Comparing Solar Quotes
The most expensive mistake is comparing final prices across quotes with different system sizes or hardware tiers. It feels efficient, but it compares nothing meaningful.
Other errors we see often:
- Ignoring inverter efficiency and warranty length
- Treating a verbal output estimate as a guarantee
- Skipping the site assessment and accepting a remote quote
- Failing to check whether the battery is CEC approved
- Choosing on price alone and discovering exclusions after signing
Normalise every quote to the same system size, hardware tier and inclusion list before you compare a single dollar figure. That one step eliminates most of the risk.
From Quote to Install: What Happens After You Sign
After signing, a compliant installer completes a site assessment, finalises the design, lodges the grid connection application and schedules installation. Timelines vary with network approval queues and roof complexity, so ask for a realistic window rather than a best-case one.
Once installed, the system needs commissioning, a Certificate of Electrical Safety and confirmation that smart monitoring is live. This is where many homeowners are left alone. Post-installation performance monitoring is the step most guides skip entirely: without it, you cannot tell whether your system is producing what the quote promised.
Verify the System Against the Quote
The quote you signed contains an estimated annual output figure in kWh. That number is your benchmark. Here is how to check it:
- Wait for a full billing cycle. Give the system at least one full month of uninterrupted operation before drawing conclusions.
- Read the monitoring app. Most inverters ship with a monitoring portal that reports daily, weekly and monthly generation in kWh. Record the monthly total.
- Compare against the quote. Divide the quoted annual figure by twelve to get a monthly average. If actual generation sits well below that average for two or three consecutive months in good weather, something is wrong.
- Check for the obvious causes first. Shading that was not modelled, a string wired incorrectly, a tripped inverter, or panels installed at the wrong tilt are the most common culprits.
- Put the concern in writing. Email the installer with the monitoring data attached and ask for a written explanation. A reputable installer will investigate; a poor one will stall.
Your quote’s estimated annual output figure is a contractual benchmark, not a marketing claim. Track it monthly for the first year and raise any shortfall in writing while the workmanship warranty is still active.
What Good After-Sales Support Looks Like
After-sales support is where installers separate themselves. Ask these questions before you sign, not after:
- Who do I call if the inverter faults, and what is the response time?
- Is monitoring included for the life of the system, or is there a subscription?
- If the installer ceases trading, who honours the workmanship warranty?
- Are replacement parts held locally, or does every fault trigger a weeks-long wait?
- Will you provide a written performance review at the twelve-month mark?
A written twelve-month performance review is uncommon but valuable. It forces a comparison between the quoted output and the actual output while the system is still under warranty, and it gives you documentation if a dispute arises later.
Plan for the Battery and the Next Decade
A solar system is a fifteen-to-twenty-five-year asset, and the inverter is usually the first major component to need attention. Ask your installer what the replacement path looks like: whether the inverter can be swapped for a hybrid unit later, whether the switchboard has capacity for a battery, and whether the mounting rails can take additional panels.
If you want a quote built around your actual roof and usage, connect with our team and we will walk you through the numbers before you commit.
Frequently Asked Questions
What should be included in a professional solar installation quote?
A complete quote should list panel and inverter brands with model numbers, system size in kilowatts, mounting hardware, isolators, cabling, and labour. It must state the STC rebate value, total installed price, and any exclusions such as switchboard upgrades or tree trimming. Ask for the CEC accreditation number of the installer and the designer. A quote without these details is an estimate, not a fixed offer.
How do government rebates affect the final solar quote price?
The federal STC rebate is usually deducted upfront by the installer, so the quoted price already reflects the discount. The number of STCs depends on your system size, location, and installation date. The Cheaper Home Batteries Program may also reduce battery costs. Always confirm whether the quoted price is after rebates and ask for the STC calculation in writing. Rebate values change over time, so check current rates before signing.
How can I tell if a solar installer is CEC-accredited?
Search the Clean Energy Council’s online directory for the installer’s name or accreditation number. A CEC accredited installer has completed approved training and must follow the CEC Code of Conduct. Ask for their accreditation card and confirm it covers both design and installation. Only CEC accredited installers can issue STCs and connect your system to the grid, so this step protects your rebate and safety compliance.
Are there hidden costs to look for in solar installation quotes?
Common hidden costs include switchboard upgrades, meter box relocation, roof repairs, scaffolding, and after-hours installation. Some quotes exclude the cost of grid connection or the removal of old systems. Read the exclusions section carefully and ask for a fixed price that covers everything. If a quote seems unusually low, check what has been left out, because those extras can add hundreds or thousands to the final bill.
How do I compare solar quotes with different panel brands?
Normalise each quote by comparing total installed price per kilowatt, panel efficiency, inverter type, and warranty terms. Tier 1 panels from established manufacturers usually offer better degradation warranties. Check whether the inverter is a string or microinverter model and how it handles shading. A quote comparison spreadsheet can help you list these variables side by side so you compare like with like.
What is the difference between a quote and an estimate for solar installation?
A quote is a fixed price offer that the installer is bound to honour for a set period, usually 14 to 30 days. An estimate is a rough guide that can change after a site assessment. Always ask for a written quote that includes the total installed price, STC rebate deduction, and a clear list of inclusions and exclusions. An estimate is not a contract and should not be used to compare installers.
Comparing solar quotes well comes down to discipline: normalise the data, verify accreditation, and read the contract before the price. GridFree Solar handles that work for you, from CEC accredited installation and rebate guidance through to CEC approved battery storage and ongoing performance monitoring. Get started with GridFree Solar and see what your roof can actually produce.