5kW vs 10kW vs 15kW Solar System Cost Compared

System size is the single biggest lever on your total solar bill. Here's what three common sizes actually cost and produce, and how installers decide which one fits your home.

5 kW system

At the national average of roughly $2.68/watt, a 5 kW system runs about $13,400 before any state incentive, producing roughly 6,000-7,500 kWh per year depending on your state's sun hours. This size typically fits a smaller home, a household with modest electricity usage, or a partial-offset strategy where solar covers a meaningful chunk of the bill without eliminating it.

10 kW system

A 10 kW system costs roughly $26,800 before incentives at the national average, producing 12,000-15,000 kWh annually — enough to fully offset a typical single-family home's usage in most states, including moderate air conditioning or a partial EV charging load. This is the most common size quoted for average-usage households in 2026.

15 kW system

At roughly $40,200 before incentives, a 15 kW system is sized for larger homes, high-usage households (pools, multiple EVs, electric heating), or homeowners intentionally oversizing to bank summer credits against winter usage in a strong net-metering state. Price per watt often drops slightly at this size since fixed soft costs (permitting, interconnection paperwork) spread across more capacity.

How installers actually size your system

The starting point is your trailing 12 months of electricity usage (in kWh), divided by your state's average peak sun hours, then adjusted up roughly 10-20% for system losses (inverter conversion, wiring, dust, imperfect angle). A homeowner planning a future EV or heat pump should tell the installer that upfront — sizing for today's usage only means paying for a second, more expensive add-on project later.

Bigger isn't always better financially

In states with weak net metering (avoided-cost export rates), an oversized system exports a lot of low-value surplus power, which drags down the blended payback period. In those states, sizing closer to your actual daytime usage — or adding a battery instead of more panels — is often the better financial call. See our net metering guide for how your state's export rate should shape sizing decisions.