I'm in the planning stages of a project that's more or less a grid tie inverter, except it does not export to the grid. There are two units involved in the part under discussion - the inverter itself that connects via a dedicated 240V circuit and a current sensor that installs in the breaker box. The tricky part is how to send the current measurements (split phase, two sensor coils) from the sensor to the inverter without requiring the installation of extra wiring. It must be low latency (less than 1ms) so that the inverter can instantly supply power to offset arbitrary loads. (In practice, it will still allow the grid to supply a small amount of the power - a few % or so, in order to enforce the zero export requirement and ensure that it shuts down if the grid goes down.)
I'm thinking of transmitting a pair of RF carriers (one for each phase) FSK modulated by Delta Sigma bitstreams or even just a pair of analog FM carriers, but now I'm wondering if some more sophisticated modulation scheme might be more robust and still meet the low latency requirement. If it helps, the inverter is going to use a FPGA for real time control, but the sensor should be kept simple mostly to avoid failure mechanisms and bugs that arise from sophisticated embedded code.
BTW, it's part of a personal project, not a product for sale.