PV stands for photovoltaic, the technology inside solar panels that converts sunlight to electricity. System size refers to the combined rated output of all the panels installed, measured in kilowatts (kW). A 10 kW system has panels rated at a combined 10,000 watts under standard test conditions.
Size affects cost, roof space required, and how much of your electricity bill the system can offset. In North Carolina, a well-sited 1 kW of panels produces roughly 1,200–1,400 kWh per year. A 10 kW system would produce 12,000–14,000 kWh annually — enough to cover most or all of an average NC household’s consumption of around 11,500–12,000 kWh per year.
The right size isn’t the biggest system that fits on your roof. It’s the system sized to your actual usage pattern. For new Duke Energy customers on the avoided cost rate, producing significantly more than you consume means exporting cheap power rather than using it. A load analysis and honest usage review from your installer should drive the sizing decision.
When you’re getting quotes
Ask each installer to show you how they arrived at the system size they’re proposing. They should reference your actual annual kWh consumption from your Duke Energy account and a production estimate based on your roof’s specific characteristics. If a proposal doesn’t reference your usage data, ask for a revised one that does. Also ask what happens to surplus production — under current Duke Energy rules, the answer affects the financial case for the size they’re recommending.
Common questions
- What size solar system do I need for a home in Raleigh or Charlotte?
- The starting point is your annual electricity consumption in kWh, found on your Duke Energy bill. Divide that number by roughly 1,200–1,400 to get an estimated system size in kW. A typical NC home using 12,000 kWh per year would need approximately an 8–10 kW system. The right size also depends on your roof area, orientation, shading, and whether you want to offset your full bill or just a portion of it.
- How is PV system size measured, and what does it mean on a quote?
- PV system size is measured in kilowatts (kW) of DC panel capacity. A "10 kW system" means the panels are rated to produce 10 kW under ideal laboratory conditions. Actual output is lower due to heat, angle, shading, and inverter losses. Installers estimate annual production in kWh using tools like PVWatts, which accounts for your location's sun hours and typical weather — central NC averages about 4.5–5 peak sun hours per day.
- Is a bigger solar system always better in North Carolina?
- Not under current rules. New Duke Energy customers (interconnected after October 2023) receive the avoided cost rate for power they export, which is well below retail. Oversizing your system means you're producing surplus power that earns very little. The better approach is to size for your actual consumption and add a battery if you want to capture excess production rather than export it. Your installer should size to your usage, not to maximize panel count.