U.S. Treasury pays for part of $11.8 million Boeing solar roof - South Carolina Electric & Gas Co. has received a $3.5 million grant from the federal government to offset the approximately $11.8 million it cost to install solar panels on the roof of Boeing's final assembly building in North Charleston last year.

$11.8mn for 2.6MW amounts to $4,540 per KW.  For a rooftop array, the capacity factor is between 15 and 20%.  Let's be generous and say 20%.  Over a 20 year life, neglecting O&M, the cost of electricity from the installation will be $130 per MWh.  Boeing will still have to buy fuel to heat the building in winter and electricity (and probably fuel) to run chillers in hot weather; and, they will still have to buy electricity to run the facility when the sun is down or low in the sky.

Just the taxpayer contribution of $3.5mn would have built a natural gas engine combined cycle plant to supply the electricity and would have, in a CHP arrangement, provided steam to provide heat in cold weather and to run an absorption chiller or ammonia chiller to provide cooling in hot weather thereby saving electricity and fuel purchases.  Overall energy efficiency would have been in the 85 to 90% range instead of the 40 to 45% of a modern coal-fired plant or 35 to 40% of a simple cycle gas turbine running to replace the output lacking from the solar facility.