As an HVAC engineer I see a massive opportunity to design building integrated PV to match the demand side. I suggest "west is best" outlook for facade PV to reduce demand late afternoons in summer.
OpenStudio's results-viewer is very powerful in partially answering my question ... just select the two meters and right-mouse options appear to subtract as required.
But how do we make a net-meter (PV generation - loads) measure to write a report on export to the grid?
That is what a homeowner gets paid for if they have a good contract from the power network.