What Does a 4 kW Solar System Cost?
This 4 kW job carries $200 of fixed cost before a single unit of work is priced, and that block is 2% of the low estimate. It is why the per-kW figure here ($2,850 at the low end) is where it is rather than somewhere near the national average.
Adjust for your state
Fixed costs of $200 are included in every figure on this page, so the per-square-foot price falls as the job gets bigger.
How it compares with the next size
Going up from 3 to 4 kW adds $2,800 to $3,200 to the bill, but the per-kW price actually falls from $2,867 to $2,850. You are paying more in total and less per unit at the same time — that is the fixed cost being spread thinner.
The next size up, 5 kW, costs $2,800 to $3,200 more, and brings the per-kW figure down to $2,840 — a further 0.4% saving on each unit.
What the number is made of
At 4 kW, the arithmetic is $200 plus 4 times 2800.0 to 3200.0 per kW. Because the fixed part does not move with the job, this page's per-kW figure of $2,850 to $3,250 would be different on a job of another size — and the tables below show by how much.
| Component | Low | High |
|---|---|---|
| Fixed costs (permits, delivery, setup) | $200 | $200 |
| Materials | $10,602 | $12,090 |
| Labor | $798 | $910 |
| Total | $11,400 | $13,000 |
The same size, five different states
Material prices do not change at the state line. Labor does. These five states sit at different points of the federal wage distribution for this trade.
| State | Labor factor | Low | High |
|---|---|---|---|
| Oklahoma | ×0.79 | $11,228 | $12,804 |
| Arizona | ×0.85 | $11,281 | $12,864 |
| West Virginia | ×0.92 | $11,336 | $12,927 |
| New Hampshire | ×1.08 | $11,461 | $13,069 |
| Illinois | ×1.40 | $11,720 | $13,365 |
Only the labor line moves between states. That is a deliberate limitation, not an oversight: state-level material pricing is not something we have reliable data for, so we do not pretend to.
By material
| Material | Low | High |
|---|---|---|
| Monocrystalline (standard) | $11,400 | $12,600 |
| Monocrystalline TOPCon | $12,200 | $13,800 |
| Polycrystalline | $10,600 | $11,800 |
Other sizes
| Size | Low | High |
|---|---|---|
| 3 kW | $8,600 | $9,800 |
| 4 kW ← | $11,400 | $13,000 |
| 5 kW | $14,200 | $16,200 |
| 6 kW | $17,000 | $19,400 |
| 7 kW | $19,800 | $22,600 |
| 8 kW | $22,600 | $25,800 |
| 10 kW | $28,200 | $32,200 |
| 12 kW | $33,800 | $38,600 |
Is a system this small worth it?
Only if your consumption is genuinely low. A system sized below your use leaves you buying the difference anyway.
Do I still get the federal credit?
Not if you own it. The residential credit ended for systems placed in service after 31 December 2025.
Can I expand later?
Usually yes, but the inverter and wiring have to be sized for it now or it becomes a replacement job.
Is 4 kW a large job?
It is number 2 of 8 on this page for this project. At this size the fixed costs come to $200 of the low total, which is 2% of the bill — lower than at the smaller sizes we cover.
How much does location change the price at this size?
Between the cheapest and most expensive state in the table the total moves from $11,228 to $13,365, a difference of $2,136. Only the labor line changes; material is priced nationally.
Updated October 2026