U.S. grant pays for solar farm at Chattanooga's Lovell Field airport - The biggest solar energy farm at an airport in Tennessee will go on line later this month, Chattanooga Metropolitan Airport officials said Monday.

So, let's see--$4.3 million for a 1.1MW plant, of which the taxpayers paid (involuntarily I might add) 95% or $4.085 million.  This will save the airport about $100,000 per year according to the article.  So, the US taxpayer has funded a boon for a single location owned by a city, not the federal government, so the taxpayers will never see a return on this investment.  It will take the airport 43 years to recoup the overall investment without considering inflation.  The facility may last 20 years before needing replacement of the panels.

I do not know how much electrical energy the airport itself consumes, but a 1.1MW gas engine installation would have cost roughly $1.32 million and over the course of a year would consume roughly $310,000 worth of fuel at $4 per million BTU while supplying power 24X7 for upwards of 8322 hours per year.  Waste heat from the engine could have been used to run the HVAC for the airport increasing the effective thermal efficiency of the facility and decreasing the cost of heating and cooling.  A well maintained gas engine can indeed last 40 years.