Threshold guide · the $/W band

Solar cost per watt — what's a fair $/W in 2026.

Updated May 16, 2026. Sources verified the same day. The LBNL band is anchored to the most recent Tracking the Sun report; we re-pull state-level data whenever Berkeley Lab publishes a new edition.

Take the cash price on your solar proposal. Divide by the system's DC size, in watts. The number you get is the single cleanest cost comparator anyone can hand you — and one of the few figures on the document that can be benchmarked against public data without phoning anyone. Berkeley Lab's Tracking the Sun report¹ covers 3.7 million U.S. residential systems installed through 2023, which is roughly 78% of the market. It gives us the canonical band: in 2023, state-level median residential installed price ran from $3.20/W to $5.20/W on a cash basis.

That's the floor and ceiling of a two-dollar-wide window where most of the U.S. residential market actually transacts. Where your number lands inside it — or outside it — is the start of the conversation, not the verdict.

Why cash $/W, and not financed $/W

Cash $/W is the comparator that cuts cleanly across installers. A financed total isn't the same metric — it bundles APR-based financing cost with what may also be a dealer fee baked into the cash quote (see our separate loan dealer-fees guide). Cash $/W is what you would actually pay an installer on the day of installation if you wrote a check; it's what LBNL's report measures; it's what state-level medians describe.

Compute it on every quote you receive. The math is one division. The spread across three quotes is more revealing than any of the individual numbers in isolation.

The LBNL band, in two sentences

$3.20–$5.20/W (cash basis, state-level median, 2023): where most residential solar trades in the United States. The lower end skews toward high-volume states with established competition (California, parts of Arizona); the upper end skews toward smaller markets, higher-cost-of-living states, or states with complex permitting and interconnection processes (parts of the Northeast, Hawaii, several mountain-west states).

That state-level spread is wider than most homeowners assume. LBNL notes the top-100 residential installers have a similar spread within them — installer-level medians ranged from $2.60/W to $5.90/W across the top 100, with roughly one-third of installers below $4/W, one-third between $4–$5/W, and one-third above $5/W¹. Different installers in the same market produce different $/W numbers for similar hardware.

What moves $/W inside the band

Four real factors push the same installer's price up or down by meaningful amounts. None of them are conspiracy; all of them are worth asking about.

1. System size. Smaller systems carry higher $/W because fixed costs (permits, truck rolls, design fees) get amortized over fewer watts. LBNL documents a $1.0/W difference in median price between the smallest and largest residential systems¹.
2. Equipment tier. Microinverters or DC optimizers (used on 93% of 2023 residential systems) cost more than string inverters. Premium-tier panels (high-efficiency monocrystalline) cost more than standard. Battery inclusion is a much bigger lever — LBNL's regression model shows battery storage adds roughly $1.4/W to the system price.
3. Site complexity.Steep-pitch roofs, multi-array layouts (e.g., split between south and west exposures), ground mounts, and main-panel upgrades all push $/W up. Ground mounts add roughly $0.4/W per LBNL's regression. A 200-amp main-panel upgrade isn't in the LBNL numbers but commonly adds $1,500–$3,500 to the install — which is $0.18–$0.42/W on an 8.4 kW system.
4. State-fixed effects. LBNL's regression model isolates a $2/W range across state fixed-effect variables alone — meaning the same equipment in the same configuration on a similar roof can cost meaningfully different amounts depending purely on what state you're in. The drivers are cost of living, retail electricity rates, incentive program design, solar insolation, and permitting friction.

Where $/W can lie

Three quiet ways the comparator misleads. Worth knowing before you rank three quotes side by side.

Below the floor.A $/W under $3.20 isn't automatically a steal. The cash price may not include permitting, inspection, interconnection, or sales tax — each of which gets added at contract signing or first invoice. Ask for the all-in price. The number that goes into the LBNL comparison is the total cost paid to bring the system online.

Above the ceiling.Above $5.20/W there's often a real reason — premium equipment, complex install, steep roof, small system in a high-cost market — but it's also the band where dealer-fee inflation tends to live. If the quote is financed-only and the cash price isn't on the page, the elevated number may be telling you about the loan markup more than the equipment.

Identical $/W, different systems. Two proposals at $4.10/W can pencil out to very different 25-year lifetime costs. A microinverter system trades higher upfront cost for better partial-shade tolerance and panel-level monitoring. A standard string inverter system trades lower upfront cost for simpler maintenance but worse performance under shading. $/W is the cost comparator; performance comparison requires looking at production estimates against PVWatts for your specific site.

The 10-minute test

Three steps. None require any tool the salesperson controls.

1. Compute cash $/W for every quote you have. Divide cash price by DC kW × 1,000.
2. Compare your numbers against the $3.20–$5.20 band. Note where each one lands relative to the midpoint ($4.20). Three quotes inside the band tell a different story than three quotes split across it.
3. Run the quote calculator on the best one and on the median one. The verdict logic is the same band you just used, and it surfaces other thresholds (production, payback, financing gap, tax-credit timing) at the same time.

One more thing: what your state's median actually is

The $3.20–$5.20 band is the floor and ceiling of state medians, which is a different question than your state's specific median. LBNL publishes state-level breakdowns in the full Tracking the Sun report (the data tables at trackingthesun.lbl.gov). If your quote is $4.80/W in California, you're near the top of the U.S. distribution but possibly also near or above your state's median — California typically sits in the lower half of the band. The same $4.80/W in Connecticut may be near or below the state median. Both directions matter for negotiating leverage.

The framing question for any cost-per-watt conversation: relative to my state's 2023 median, is this number high, low, or normal — and if it's high, what specifically about my install justifies the spread? If the answer is a list of real items (steep roof, MPU, complex layout), that's a price you can negotiate against. If the answer is hand-waving, the spread is the markup.

What this guide doesn't cover

The financed-side markup that often sits behind a low APR (see loan dealer fees). The lifetime-cost picture, which depends on production estimates and utility-rate escalation that don't show up in $/W. Whether the system is sized correctly for your roof and usage (that's the system-size question, not the $/W question). For the audit that connects all of these, the quote calculator runs every threshold above and surfaces the financed-side gap and the production sanity check in one pass.

1. 1. Berkeley Lab, "Tracking the Sun, 2024 Edition" (Executive Summary, August 2024; data through year-end 2023; sample ~3.7M U.S. distributed PV systems). State-level median residential installed price in 2023: $3.20–5.20/W. Loan dealer-fee gap, verbatim: "a large portion of residential systems are loan-financed, and installed prices reported for these systems likely include dealer fees, adding anywhere from 5-50% to the total up-front price paid by the customer." Verified 2026-05-16. emp.lbl.gov · Tracking the Sun 2024 (PDF) ↩
2. 2. EIA Electric Power Monthly, Table 5.6.A — Average Price of Electricity to Ultimate Customers by End-Use Sector. February 2026 residential average: 17.65 ¢/kWh, +7.4% year over year vs February 2025. 10-year residential rate trend: ~2–3% per year. Released April 23, 2026. Verified 2026-05-16. eia.gov/electricity/monthly ↩

Next: What the financed price hides — when the cash $/W isn't the cash $/W.