A solar quote arrives as one number for one system, and one number cannot be compared to another. Divide the total by the system's DC watts and you get dollars per watt — the unit the industry actually prices in, and the only figure that survives the fact that one installer quoted 7.2 kW and another quoted 9.6 kW.
A 9.6 kW system at $26,880 is $2.80/W. A 7.2 kW system at $21,600 is $3.00/W. The smaller system is the more expensive one, and the totals say the opposite.
What it costs
Residential rooftop, installed, before any incentive, typical US pricing at the time of writing:
| System size (DC) | Typical $/W | Typical installed |
|---|---|---|
| 4 kW | $3.10 – 4.20 | $12,400 – 16,800 |
| 6 kW | $2.90 – 3.80 | $17,400 – 22,800 |
| 8 kW | $2.70 – 3.50 | $21,600 – 28,000 |
| 10 kW | $2.60 – 3.40 | $26,000 – 34,000 |
| 15 kW | $2.40 – 3.10 | $36,000 – 46,500 |
Typical US installed pricing at the time of writing, not quotes. Get three.
The federal residential clean energy credit takes 30% off the installed cost for systems placed in service through 2032 — check current eligibility and your own tax position before counting it, because it is a credit against tax owed rather than a rebate. State and utility incentives sit on top and vary enormously.
Why the unit price falls with size
Roughly half of a solar installation does not scale with the number of panels:
- Permitting, interconnection paperwork and inspection are the same for 4 kW and 14 kW
- The crew mobilises once either way
- The main service panel work, conduit run and shutdown are near-fixed
- Design, engineering and the sales cost are fixed
So the fixed block spreads over more watts, and $/W falls. This is why "just do a small system to test it" is usually the most expensive way to buy solar per unit of output.
What is inside the number
| Line | Share of a typical installed price |
|---|---|
| Panels | ~15 – 25% |
| Inverter or microinverters | ~10 – 15% |
| Racking, wiring, disconnects, BOS | ~10 – 15% |
| Labour | ~15 – 20% |
| Permits, inspection, interconnection | ~5 – 10% |
| Overhead, sales, margin | ~20 – 30% |
The hardware is a minority of the price. That matters, because most homeowner comparison shopping is about panel brands — the part with the least leverage on the total. A cheaper panel saves a few cents per watt. A different company can differ by a dollar per watt on the same hardware.
The traps in comparing $/W
DC watts or AC watts. Always divide by the DC rating — the sum of the panel nameplates. Some quotes lead with an AC or "system output" figure that is 15–25% lower, which makes $/W look worse than it is, or better, depending on which way you were misled.
Before or after the credit. Quoting $/W net of the 30% credit produces figures near $2.00/W that are not comparable to gross quotes. Ask which one you are looking at.
What is included. A quote that excludes a main-panel upgrade, roof work, or a long conduit run is not cheaper — it is incomplete, and those items arrive later.
Panel count vs panel wattage. Twenty 400 W panels and twenty-four 340 W panels are not the same system. Compare kW, never panel count.
From cost per watt to whether it pays
Cost per watt is the input. What you get back depends on how much the array produces where you live and what your utility charges — see solar panel output per day by state and peak sun hours by state. Sizing the array to your own consumption comes first; see how many solar panels to run a house.
For the arithmetic that turns those into years, see solar payback period.
The short version
Divide every quote by its DC kilowatts and compare the result. Expect $2.40 – 3.60/W installed on a typical residential job, expect the number to fall as the system grows, and remember that the hardware you are shopping is a fifth of what you are paying for.