Solar System Size & Cost
The four sizes most US homeowners shop for — 5, 8, 10 and 15 kW — with typical gross prices, production, panel counts and state-level data. National planning median: $2.80/W cash, before incentives.
The federal residential solar tax credit (30% §25D) ended December 31, 2025.
Under the One Big Beautiful Bill Act, systems placed in service on or after January 1, 2026 do not qualify for the residential credit. Systems installed and operational by December 31, 2025 can still be claimed at 30% on the 2025 return. Commercial and third-party-owned (lease/PPA) projects may qualify under §48E — see the federal incentives page.
Status verified 2026-08-21. Confirm your circumstances with a qualified tax professional.
5 kW
$12,500–$16,000
gross · 11–12 panels (400–450 W) · ≈5,500–8,500 kWh/yr depending on state sun
8 kW
$20,000–$25,600
gross · 18–20 panels (400–450 W) · ≈8,800–13,600 kWh/yr depending on state sun
10 kW
$25,000–$32,000
gross · 22–25 panels (400–450 W) · ≈11,000–17,000 kWh/yr depending on state sun
15 kW
$37,500–$48,000
gross · 33–38 panels (400–450 W) · ≈16,500–25,500 kWh/yr depending on state sun
Sizing in one paragraph
System size = annual kWh you want to offset ÷ how much energy each installed kW produces where you live. A home using the US average (~10,100 kWh/yr) in a region producing ~1,400 kWh/kW/yr needs roughly 7–8 kW. Bigger homes, EVs, heat pumps and pools push you toward 10–15 kW; small homes or partial offsets can work at 5 kW. Use the system size estimator for your own numbers.
Why $/W matters more than size
Compare quotes by price per watt (total price ÷ watts), not total price — a 10 kW system naturally costs more than an 8 kW system. Larger systems usually have slightly lower $/W because fixed costs (permits, travel, sales) spread over more watts. But a bigger system only pays if you use (or are fairly paid for) the extra production.