The cost of solar panels per kW can vary significantly based on several factors, including the type of solar technology, the scale of the installation, geographical location, and installation costs. On average, the cost of solar panels has seen a remarkable decline over the past decade due to advancements in technology, increased competition, and economies of scale. As of recent data, the cost averages around $2.50 to $3.50 per watt. Therefore, a typical residential solar panel system with an average size of 6 kW could range from $15,000 to $21,000 before incentives like tax credits or rebates.