The average cost of a 12 kW solar panel installation on EnergySage is $30,505 before available incentives. You'll typically save anywhere from $37,000 to $148,000 over 25 years by installing solar panels. 30 per watt in 2025, representing a 60% decrease from 2010 levels. solar calculator — enter your ZIP code and electricity bill, and it returns your recommended system size in kW, the number of panels, the roof area you need, the gross install cost, the annual savings, the payback period, the 25-year lifetime profit, and the CO₂ offset. Built on. NLR analyzes the total costs associated with installing photovoltaic (PV) systems for residential rooftop, commercial rooftop, and utility-scale ground-mount systems.