A residential rooftop solar PV system in Los Angeles, CA, has a cheaper cost per kilowatt-hour of electricity delivered than the most cost effective, utility-scale concentrating solar power plant. 

In 2010, a buying group called Open Neighborhoods openly advertised an opportunity to get a solar PV system installed for $4.78 per Watt (not including any tax credits, rebates, or grants), a system that would produce approximately 1,492 kilowatt-hours (kWh) per year (AC) for each kilowatt of capacity (DC). 

Based on the best available public information about the costs and performance of operational concentrating solar thermal power plants, the PS10 solar power tower – an 11 MW installation in Spain – has the lowest levelized cost of operation of any concentrating solar power plant that produces electricity.  PS10 had an installed cost of $4.15 per Watt and produces 2,127 kWh per kW of capacity. 

However, due to higher operations costs and a higher cost of capital (8% rather than 5%) for a concentrating solar power plant, the levelized cost of the residential rooftop system (17.3 cents per kWh) is less than that of the power tower (19.9 cents per kWh).

This analysis also does not include any transmission infrastructure or efficiency losses, either of which would increase the levelized cost of the concentrating solar power plant.  It also did not include the lower price point from Open Neighborhoods, which advertised a possibility of driving the price down to $4.22 per Watt (driving the levelized cost down to 15.3 cents per kWh).

The Southern California Edison project, also featured in the chart, is another example of low-cost distributed solar PV, with the 250 MW project spread across commercial rooftops in 1-2 MW increments but still achieving large scale. 

It's possible that concentrating solar power will see cost reductions as more projects are developed.  After all, so far there have been just over 20 projects built for a combined capacity of 1,000 MW, whereas Germany alone installed 3,000 MW of PV on thousands of rooftops in 2009.  But PV costs are also declining, making the competition for concentrating solar that much fiercer and the potential for distributed solar that much greater.