In 2017, most homeowners are paying between $2.87 and $3.85 per watt to install solar, and the average gross cost of solar panels before tax credits is $16,800. Using the U.S, average for system size at 5 kW (5000 watts), solar panel cost will range from $10,045 to $13,475 (after tax credits). That’s nine percent lower than it was a year ago, and solar panel system costs are continuing to fall.