The system
Start from a common residential size, then replace module count and watts with the layout you actually drew.
The roof and the service
Roof factor multiplies array labor only. Electrical extras are a fixed hour-and-material adder — they do not get cheaper on a smaller array.
Your costs
Payroll burden covers employer taxes, workers’ compensation, liability insurance, and paid time off. Matching a cheaper per-watt quote after leaving it out is how a sold job becomes a loss.
Hand the customer a proposal
The price above is for you. This is the page you print or save as a PDF and give to the customer — your details, their details, the scope, the deposit split, and a line for them to sign. Your business details are saved on this device so you only type them once; the customer’s details are never saved.
Everything on the printed page is text you typed or a number this calculator worked out. It contains no warranty, lien, or cancellation wording — those depend on your jurisdiction and your contract, and this tool is not the place to invent them.
Your bid
- System size
- Crew hours
- Loaded labor
- Equipment
- Electrical & battery extras
- Permits, design, travel
- Overhead
- Total cost
- Profit
- Price per watt
- Effective hourly rate
- Walk-away price
- Walk-away $/W
Where the cost goes
Transparent arithmetic from your own inputs. Roof factors and electrical extras are common ballpark starting points, not an industry standard, a benchmark, or a guarantee. Time your own crews and replace them.
Common questions
Why does a dollars-per-watt quote go wrong?
Because only part of a solar job scales with watts. Modules, racking, and balance-of-system do. Roof difficulty and electrical work do not — and they are the two lines that decide whether the job made money. Two 10 kW installs priced at the same $/W can differ by thousands: one on a clean composition roof with room in a 200 A panel, the other on tile needing a 100 A → 200 A service upgrade. This tool prices watts as watts and prices the rest as its own hours and material.
How much does the roof type actually change labor?
It multiplies array labor hours: composition at 4/12–6/12 is the 1.0 baseline, 7/12–9/12 is 1.18, 10/12 or steeper is 1.35, multiple arrays or hips and valleys 1.25, tile or slate 1.45 (hooks and flashings), and ground mount 1.4 (piers and trench). Metal standing seam is the one that goes down, to 0.95, because clamps beat penetrating and flashing. These are starting points for your own crew, not an industry standard — retime them from your last few jobs.
Which electrical extras get forgotten most often?
The panel. A supply-side or load-side tap is about 4 h and $350; a 100 A → 200 A main-panel upgrade about 8 h and $1,800; a 200 A → 400 A service upgrade about 16 h and $4,500. A new subpanel or inverter feeder, 50+ extra feet of conduit, and a trench to a detached structure each carry their own hours and material. None of these move with system size, which is exactly why a per-watt price cannot carry them.
Where do permits, interconnection, and design go?
They are their own flat lines — permit and interconnection, design and engineering, and travel/dumpster/lift — not a percentage of the system. Sizing, production estimates, shading analysis, incentive eligibility, and interconnection approval are all outside what this does: it is bid arithmetic on inputs you supply, not a PV design, a production model, or a claim about what any utility will approve.
Does adding a battery just add its price?
No, and that is why battery hours and battery material are separate fields. The hardware is one cost; the mounting, the critical-loads panel, the commissioning, and the extra inspection are labor that lands on the same crew day. Entering only the equipment cost is the same mistake as the per-watt quote, one level down.
Why isn't a 20% margin the same as adding 20% to my cost?
Margin here is a share of the final price — price = job cost ÷ (1 − margin) — which is how the customer's number reads and how your books read it. Overhead is a separate markup on direct cost, applied before margin and never to itself or to profit. A $18,000 cost marked up 20% is $21,600, a 16.7% margin; a 20% target margin is $22,500. No account, no upload: every figure stays in this browser, and the optional local counter records only which features were used and the day.