Solar Cost
Solar System Cost Estimator
Build a costed bill of materials for a solar system
Updated July 12, 2026 · Live
What this tool does
Builds a costed bill of materials for a solar system — panels, batteries, inverter, controller, mounting, cabling and labour — with a contingency and cost per kW.
Enter the quantity and price of each component plus labour and a contingency; the calculator totals the bill of materials and the cost per kW.
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Formula Used
How the solar system cost estimator works
Each line is a quantity times a unit price — panels and batteries — plus the single-item prices for the inverter, controller, mounting and cabling, and your labour figure. The subtotal is grossed up by the contingency to a total. Dividing the total by the system size in kW, from panel count times wattage, gives a cost per kW you can compare against quotes.
What you enter
Enter the quantity and price of each component plus labour and a contingency; the calculator totals the bill of materials and the cost per kW. Every field is editable, and the result recalculates the moment you change a value.
Reading the result
The line-by-line breakdown is the value here: it shows where the money goes and lets you swap a component and see the total move. The cost per kW is the headline figure installers and comparison sites quote.
Safe by design
This calculator does the arithmetic of sizing — quantities, geometry and cost. It deliberately stops at the line a certified installer must sign off. It will never tell you a cable or fuse size, an earthing arrangement, a battery charge voltage, or a roof structural load: those are regulated calculations where a wrong number causes fire, electrocution or collapse. All electrical work must be carried out by a qualified, certified installer, and this page is not an installation guide.
Assumptions and limits
Every price is your own — nothing is embedded, because component prices move constantly and vary by supplier and market. The estimate covers hardware and labour you list; it does not include scaffolding, grid-connection paperwork or any grants, which differ by location.
Using it with the rest of BuildMetricLab
This calculator is one step in planning a system. Pair it with the other solar sizing, geometry and cost tools to go from an energy figure to a panel count, a layout and a costed bill of materials. Every BuildMetricLab tool runs entirely in your browser — no sign-up, nothing sent to a server, and the formula is shown on the page so the maths can be audited.
Sources & methodology
Builds a costed bill of materials for a solar system — panels, batteries, inverter, controller, mounting, cabling and labour — with a contingency and cost per kW. Every result is calculated from the values you enter, all inputs are editable, and no time-sensitive prices or tariffs are embedded.
Frequently asked questions
Why do I enter my own prices?
Component and labour prices change constantly and vary by supplier and country. Entering your own quotes keeps the total accurate rather than baking in a figure that goes stale.
What contingency should I add?
A 10–15% contingency covers extra fixings, access difficulties and the odd surprise. Complex or first-time installs justify the higher end.
What is cost per kW?
It is the total divided by the installed panel capacity. It is the standard way to compare one quote against another regardless of system size.
Does this include grants or grid fees?
No. Grants and grid-connection charges vary by location and change over time, so they are left out. Add or subtract your own local figures separately.
Spotted something off?
Calculations or display — let us know.