Mainly the cost to the customer is being reduced through gov't subsidy if you can get it. The cost of solar cells does not appear to be moving, hasn't moved in 1/4 century.
“# More concentrated ‘solar power plants’ will be built in the Southwest, providing clean electricity for millions of homes and businesses around the region. According to Sandia National Labs, costs are predicted to fall to about 5 cents per kilowatt-hour by 2020, a price competitive with new coal- or gas-fired power plants.”
http://www.nrdc.org/air/energy/renewables/solar.asp