A solar panel’s price depends on many factors, such as the type of solar panel, size of the system, rated power of each solar panel, and other technical issues. The average cost of monocrystalline solar panels, which are the most energy-efficient option on the market, starts from $1 per watt up to even $2 per watt. This price only includes the cost of the solar panels. The cost of a complete solar panel system with all the other parts like inverters, wires, mounting systems, and other things is usually between $3-4 per watt. To sum up, solar panels cost can be different depending on the solar panel brand, number of panels, and their type. Building a more advanced system with battery backup increases the system price.