Residential solar is priced per watt, not per panel. Most installed systems land around $2.50–$3.50 per watt before any incentives, so a typical 7 kW system runs about $17,500–$24,500. Size is the biggest lever: the cost per watt falls as the system grows, because permits, design, and the crew turning up cost roughly the same either way.
What affects the price
System size (kW)
The dominant factor. Bigger systems cost more in total but less per watt, because fixed costs spread further.
Roof complexity
A simple south-facing plane is cheapest. Steep pitch, multiple planes, dormers, tile or slate, and limited access all add labor.
Inverter type
A string inverter is cheapest; microinverters or optimizers cost more but handle shading and per-panel monitoring better.
Electrical upgrades
An older service panel often needs upgrading before it can take solar — commonly $2,000–$4,000 on its own.
Battery storage
Adding a battery typically adds $10,000–$15,000. It is a separate decision from the array, and it is what most quotes differ on.
Permitting and interconnection
Varies enormously by jurisdiction and utility, and the timeline varies more than the cost.
Cost breakdown
National-average planning ranges — your local pricing varies by region, scope, and access.
DIY or hire a pro?
Not a DIY job. Roof penetrations, a licensed electrician for the service connection, permits, utility interconnection approval, and inspection are all required — and most incentive programs require a licensed installer to qualify at all.
Estimating this job?
Use the free size a solar system, then turn it into a priced quote your customer can approve with the free estimate generator.
FAQ
How much do solar panels cost per watt?
Roughly $2.50–$3.50 per watt installed before incentives for a residential system in most of the US. Multiply by system size in watts: a 7 kW system is 7,000 watts, so about $17,500–$24,500. Commercial installs come in lower per watt because of scale.
How many solar panels do I need?
It depends on your annual usage, your roof, and how much sun the site gets. A common residential system is 6–10 kW, which is roughly 15–25 modern panels at 400 W each. Start from your last twelve months of kWh rather than from a panel count.
Is there still a federal tax credit for solar?
A federal residential clean energy credit has covered a substantial share of system cost, but both the rate and the eligibility rules have been changed more than once by legislation, and state and utility incentives vary on top of that. Check current IRS guidance and your state program before relying on a specific figure — anyone quoting you a credit as though it were fixed is not being careful.
Does a battery make sense?
A battery adds roughly $10,000–$15,000 and does not usually pay for itself on energy arbitrage alone. It makes sense where outages are frequent, where net metering is poor or being withdrawn, or where time-of-use rates are steep. Treat it as a resilience purchase, not a savings one.
What is the payback period?
Commonly 7–12 years, but the spread is wide because it depends almost entirely on your electricity rate and your sun. High-rate, high-sun regions pay back fast; low-rate, cloudy ones may never. Ask any installer to show the calculation using your actual utility rate rather than a national average.