Section 25 of the federal residential Investment Tax Credit drops to zero on Jan. 1, 2017 -- a short 13 months from now. Effectively, the after-incentive selling price to residential homeowners will go up by 30 percent. A typical 5-kilowatt system at $4 per watt will increase in price from $14,000 (with the 30 percent ITC) to $20,000. It doesn’t take a degree in economics to conclude that residential sales will plummet. Indeed, GTM and SEIA expect that it will take several years to find $1.20 per watt in cost savings in order to resume the pace of installations in 2016, writes Barry Cinnamon, who runs Cinnamon Solar, a local San Jose installer, and Spice Solar, a provider of technology and components for integrated racking solar modules. He is a Board of Directors alternate at SEIA, former president of CALSEIA, and founder of Westinghouse/Akeena Solar.