On average, a 3 kW solar panel system costs $9,150, according to real-world quotes on the EnergySage Marketplace from 2025 data. But your actual price will depend on factors like your roof's complexity, local labor costs, the equipment you choose, and what incentives are available in your area., which pays you for the excess solar electricity you send to the grid. This estimate is based on a household experiencing average UK irradiance with a 3. That's approximately 3,600 to 4,300 kWh per year, depending on where you live and your sun exposure. What is a 3-kW solar system? A 3-kW solar system is made up of solar panels. The cost of 3kV solar energy systems can vary significantly based on multiple factors such as location, installation specifics, and equipment selection.