Price the job from cost, then convert to dollars per watt. Do not start from a published $/W and work backwards. Two 10 kW residential arrays can differ by several thousand dollars once the roof and the electrical service are in the bid.
Modules, inverters, and racking mostly scale with watts. These do not:
Steep pitch, tile or slate, hips and valleys, or a second array
A 100 A → 200 A (or 200 A → 400 A) service upgrade
A long AC/DC run, a trench to a detached structure, or a ground-mount pier field
Permit, interconnection, and utility fees that are a trip and a check, not a watt
A battery or backup adder sold on the same visit
If you match a cheaper $/W quote that was written for an easy composition roof and a clean 200 A panel, you are matching someone else's job, not yours.
A bid that holds together
Size the array from module count × watts, not a rounded marketing kW.
Time array labor as hours per kW on an easy roof, then multiply by a roof factor.
Add electrical extras as their own hours and material. They do not shrink when the array is smaller.
Load the wage (taxes, workers' compensation, insurance, PTO). Price from loaded labor, not take-home.
Add permits, design, travel, dumpster, and lift.
Recover overhead as a percent of direct cost, then set margin as a share of the customer's price.
Only then look at $/W — and at the walk-away price if a closer asks you to sharpen it.
What this is not
This is not a structural stamp, an interconnection approval, a code inspection, a payback model, or tax or incentive advice. It is arithmetic on numbers you enter. Confirm layout, AHJ and utility requirements, and every invoice before you send a price.
Common questions
How much should I charge to install solar panels?
Charge from your own cost: modules, inverter, racking, BOS, crew hours times a roof-difficulty factor, electrical extras, permits, overhead, and the margin you intend to keep. Convert that price to dollars per watt at the end for comparison, not as the bid method.
Why is a dollars-per-watt quote dangerous?
Equipment scales with watts. Tile hooks, steep pitch, multiple arrays, and a 100 A to 200 A panel upgrade do not. Those extras can erase the margin on a quote that looked fine on a composition-roof job of the same size.
Does this include tax credits or utility incentives?
No. The calculator prices the install. Incentives, rebates, and tax credits are the customer's, the accountant's, or the program administrator's to apply. Do not treat the tool as a net-cost or payback determination.