For all of our buildings with renewable energy systems, we employ a net metering method.  We deduct the energy supplied by the system from the building load on the campus grid.  So, if ECE uses about 250,000 kwh of electricity per month, and the rooftop array will supply 10,000 kwh per month, then the net bill for the ECE building will be 240,000 kwh at the campus electricity rate.  Therefore, the building gets full credit for the energy supplied by the array.