Estimating Software for Solar Installers

System size in kW and the number of panels is the starting point for every solar quote, and it comes from counting panels off a roof layout plan or from a site assessment — the same way any other trade counts components before pricing them, rather than estimating a round number and working backwards.

Once the panel count and system size are set, the inverter follows — sized to the array’s output rather than picked first. A larger system, or one split across multiple roof faces, may need a bigger inverter or more than one, which changes both the equipment cost and the labour to mount and wire it. Getting the panel count right from the plan avoids re-pricing the inverter line later.

Mounting and racking hardware — rails, brackets, flashing and fixings — needs to be priced against the actual roof type, because a tile roof and a tin or metal roof are genuinely different jobs, not a shared rate with a small adjustment.

Tile roofs typically need tile hooks or replacement tiles, more careful flashing and sealing around each fixing point, and more time per panel to avoid cracking tiles. Tin and metal roofs are usually faster to fix to, with different fastener types and less risk of damage per fixing. Averaging these into one racking rate either over-prices the easy tin roof or under-prices the tile roof — keeping separate rate lines for each roof type in your rates library avoids both.

DC cabling runs from the panels to the inverter, and AC cabling runs from the inverter to the switchboard, and both are lineal-metre items that grow with roof size and the physical distance between components — not a fixed cost regardless of how the roof and switchboard are laid out.

A longer DC run across a large or split roof, or an inverter located well away from the switchboard, means more cable, conduit and fixing time than a compact, single-face install. Isolators are also part of the job at various points along the run, and switchboard work — fitting a new circuit breaker, or upgrading an older board that has no room for one — is its own line item, since an older switchboard can add real time to a job that otherwise looks straightforward.

A meter or grid-connection allowance covers the metering change and network provider paperwork that comes with connecting a new solar system, and it belongs in the quote as its own line rather than being assumed as included in the installation labour.

Access, height and travel are the costs most likely to be missed on a quote built from a single average rate. A steep or multi-storey roof needs more time, and sometimes different equipment, to work safely than a single-storey job with easy ladder access. Jobs further from the installer’s base add travel time and cost too. Pricing these as a deliberate allowance, rather than folding them into the racking or cabling rate, keeps the quote accurate whether the job is a simple bungalow roof or a difficult, remote one.

Rebates and small-scale technology certificates (STCs) can be included in a solar installation quote as a single deduction line that reduces the price shown to the client — the estimate only needs the dollar figure that applies to that job, not an assessment of eligibility or scheme rules.

STC values and eligibility criteria change over time and vary by system size, location and installer accreditation, so the figure used in any quote should be confirmed against the current scheme rather than carried forward from an old template or a previous job.

The table below shows how a typical residential solar installation quote is broken into line items. The rates and figures are illustrative examples only, not live pricing or a real quote — every actual job should be priced from your own current solar rates library.