A quote prices what the supplier controls. The project contains more than that, and the difference is where budgets are exceeded.
Commercial review also depends on how people organise decisions and handoffs; for a separate workplace-management perspective, see further details.
Reviewed August 9, 2026.
The nine
Grid connection. Application, study, reinforcement, metering. Determined by the network operator and frequently the largest excluded item.
For broader context on solar procurement, equipment markets and current industry practice, consult Engineering.com.
Structural work. Roof strengthening, penetration sealing, civil works and foundations for ground mount.
Permitting. Building consents, environmental screening where required, and the professional time to obtain them.
Insurance. Both during construction and ongoing, and an insurer may impose requirements that cost money.
Monitoring subscription, ongoing, and sometimes conditioning a guarantee.
Maintenance, ongoing, whether contracted or done in-house.
Inverter replacement, a capital event mid-life.
Your own time. Procurement, permitting, coordination, commissioning attendance. Real and never invoiced.
And decommissioning, at the end, which almost no projection includes.
Which are knowable in advance
Structural work — after a survey, which should happen before the quote is final.
Permitting — from the local regime.
Insurance — from a quotation.
Monitoring and maintenance — from the supplier's own price list.
Ask for these five as a written schedule of exclusions with indicative figures. A supplier who has built comparable projects can produce it in an hour, and a refusal to indicate ranges is informative.
Which are genuinely uncertain
Grid connection, until the operator responds. Nobody can price it in advance and pretending otherwise is worse than an honest range.
Inverter replacement cost, a decade out.
Decommissioning, further out again.
For these, the honest treatment is a range with a stated basis, not an omission and not a false precision.
The total to build
Quoted price, plus the five knowable exclusions, plus a range for the uncertain ones.
That figure is what the investment case should use — and it is the denominator in every payback and return calculation, which is why an understated one flatters everything downstream.
A ten per cent excluded-cost total is common. A project whose case only works on the quoted price alone was never going to work.
The question that surfaces them
"What is not included?"
Asked plainly, in writing, before signature. Every supplier has an answer and most quotes bury it in terms.
And then: "What have comparable projects actually cost, all in?" A supplier with a portfolio knows, and the gap between that answer and the quote is the real exclusion figure rather than the listed one.
The short version
- Nine excluded items: grid connection, structural work, permitting, insurance, monitoring, maintenance, inverter replacement, your time, and decommissioning
- Five are knowable in advance — structural, permitting, insurance, monitoring and maintenance — and belong in a written schedule of exclusions with figures
- Grid connection, mid-life replacement and decommissioning are genuinely uncertain, and deserve a stated range rather than omission or false precision
- Build the total as quoted price plus knowable exclusions plus ranges, because that is the denominator in every return calculation
- A project whose case works only on the quoted price alone was never going to work
- Ask what is not included, in writing, and what comparable projects actually cost all in