Solar panel cost by system size (2026)

How much does a solar system cost, by size? The table below shows the average US price for each common system size — from a small 4kW array to a large 20kW one — along with how many 400-watt panels it takes, how much energy it produces, and how fast it pays back. These are national-average figures; for your state see solar panel cost by state, or run your exact numbers in the savings calculator.

Average solar cost by system size

Based on a US-average installed price of $3/W and 4.7 peak sun hours per day. Gross cost is before any incentives — the 30% federal tax credit ended for purchases on Dec 31, 2025.

System size400W panelsAvg cost (gross)Annual outputEst. annual savingsPayback
4 kW10$11,7605,490 kWh$93312.6 yrs
5 kW13$14,7006,862 kWh$1,16712.6 yrs
6 kW15$17,6408,234 kWh$1,40012.6 yrs
7 kW18$20,5809,607 kWh$1,63312.6 yrs
8 kW20$23,52010,979 kWh$1,86612.6 yrs
10 kW25$29,40013,724 kWh$2,33312.6 yrs
12 kW30$35,28016,469 kWh$2,80012.6 yrs
15 kW38$44,10020,586 kWh$3,50012.6 yrs
20 kW50$58,80027,448 kWh$4,66612.6 yrs

National-average modeled estimates, June 2026. Not a quote — see methodology. Prices vary by state; check cost by state.

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Frequently asked questions

What size solar system do I need?
Match system size to your yearly electricity use. A 6kW system produces roughly 7,000–9,000 kWh a year in a typical US location — enough for a home using about that much. Bigger homes (or those adding EVs and heat pumps) lean toward 8–12kW. The most accurate way is to size against your last 12 months of usage with our calculator.
How is solar system size measured?
System size is the combined DC rating of all the panels, in kilowatts (kW). A system of fifteen 400-watt panels is 6,000 watts, or 6kW. It's a measure of capacity, not of how much energy you'll actually produce — that depends on your local sun hours.
Does a bigger solar system always save more?
Only up to a point. A system sized well past your usage produces excess energy that, depending on your state's net-metering rules, may be credited at less than the retail rate — so the extra panels pay back slowly. The best value is usually a system sized to roughly offset your own annual consumption.