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Initial accepted solar quotes not been fulfilled due to lack of roof space

Hi All,
Not sure if this is a ‘thing’ within the industry but I was quoted a 7.7kw system (22 Panels) and the installers turn around and say I do not have enough roof space for the panels to fit. Then company says that reducing the panels (to 21) and system to a 7.35kw and reducing the cost by $500.

I find it a bit weird when they physically came out to look at my place and quote on the system that this would fit. This has also happened to my mums place (diff company) and several friends (again different companies).

Has anyone had the same issues or anyone know if this is a ‘thing’ as in are they doing quotes properly or there is a STC scam?


Hi @jacksta. We had a similar scenario with quotes for the first of our two systems. Fortunately the issue was evident before selecting the best supplier from the quotes. I was able to get amended pricing before making the decision and assess the differences.

Unless for the quote there has been someone on your roof to measure up it is open to question if they are being optimistic to maximise your outcomes or just lazy. They all seem to rely on using a high resolution aerial image and guess of the roof pitch. Reducing the cost by $500 for one less panel seems very fair/generous.

The installing team is typically not involved with the quote. For our system the installer turned up with a full set of 24 panels when the quote and design was for 18. We installed 20. The quoted design layout was not what the installer recommended should be done. It wasted 30 minutes at the start of the day to sort out. I’d suggest it is less deliberate and more just poor management.

STC’s are based on the installed panel capacity. It’s getting close to two years since our systems were quoted and installed. I recollect receiving copies of the paperwork submitted by the supplier/installer with the STC’s and final system approvals, (not the quoted details). Hopefully these match your 21 panel install.

Changing how solar PV panels are arranged on a roof changes the amount of effort and materials (rails, brackets etc) required for the install. Subcontracts or human nature considered the best layout of panels for solar generation may not be the easiest or cheapest for the installer. Householder be well informed and have the design in black and white. Although we received quotes stating the panel arrangement was only indicative. IE subject to change on the day. The latter makes a joke of CEC accredited suppliers required to have an accredited solar system designer.


Usually in larger companies, the person coming out to do quotes is a salesperson and not the installer. They also won’t have the relevant equipment nor training to go onto your roof to do a full measurement and will often use remote sensing information like Google Earth or such like to estimate the size of a roof in question. Using remote sensing information, while gives an indication of a roof area, isn’t accurate…the biggest problem is it doesn’t give a roof slope which will affect the length of the roof available for an installation. Other features such as vent pipes, TV aerials and such like may also not show up in remote sensing information, and these can affect the number of panels installed and where they are installed. With larger companies, often they only discover the limitations (smaller roof area or vent pipe) when they access the roof for the installation.

Smaller individual installers (businesses) will often go on the roof or it will be the installer who also provides the quote. An installer will be able to get a better appreciation of the actual roof area by measurements and/or experience. The installer may also be the designer…rather than the sales person (or someone working in an office and hasn’t visited the house/roof) in larger companies. We used a independent installer in Tassie and from his experience he knew the limitations (shadows, slopes, truss configuration etc) of our roof and these were factored into the design and quote.

Also, what did your contract with the installing company say about amending design/quote at the time of installation?