Hi Nathan,
In SAM 2015.6.30 r2, when you run the the residential or commercial financial model with no net metering, SAM models the system as if there were two utility meters: One to measure the total electricity sold to the grid in each month, and one to measure the total electricity purchased from the grid in each month.
When the sell rate is zero for all time periods in a month, the meter that measures electricity sales records zero for that month, so that the value of the electricity generated by the renewable energy system for the month is zero.
This is different than SAM 2014.11.24 and earlier versions. In those versions, SAM models the no net metering scenario as if there were a single meter that can run backward: For hours that the system generation is greater than the load, the sell rate applies to the excess generation, and for hours that the system generation is less than the load, the buy rate applies to the net electricity from the grid.
For the next version of SAM, we are adding options for how SAM models net metering or no net metering: Net metering with kWh rollover, net metering with $ rollover, no net metering with hourly reconciliation, and no net metering with monthly reconciliation. We hope that will make it possible to model most utility rate structure scenarios.
Best regards,
Paul.
