My electric installation has three meters. One is total power. One is for geo in the house and one for heat pump in the shop building. The power consumed by geo and the heat pump is subtracted from the total and charged at lower rate during the heating season. If I understand interconnection agreement correctly the coop will install another meter measuring power delivered to the grid. The meters are read once a month. If there is excess compared to total power delivered from the grid it is applied as credit for next month etc. If there is still excess at the end of a year it will be converted to cash at rate 3.5 cent or whatever the wholesale rate is at that time. In other words the solar system should be sized to just cover the consumption for the best ROI.
That sounds logical, but I would get a definite answer about using net-metering and reduced heating rates in combination. Chances are, they won't do anything your state PUC doesn't require them to do.