Time sensitiveExport rules and rates are set by your municipality and change over time. Confirm the current position for your connection before relying on it.
Once the battery is full and the house is only drawing what it normally draws, a solar array on a clear afternoon has spare capacity it cannot use. What happens to that energy depends entirely on how the system was set up.
In most cases it is either exported for a modest rate, or the array simply throttles back and does not produce it at all.
The economics of export
Where export is permitted, the rate paid is typically well below what you pay to import. So a unit you export and later buy back has cost you the difference.
That gap is the entire argument for using surplus on site instead. A unit you consume yourself is worth the full retail price you did not pay.
Water heating is the obvious candidate
A geyser is a battery that stores heat instead of electricity, and most households already own one. It is a large, flexible, tolerant load. Nobody minds whether the water was heated at 13:00 or 19:00, as long as it is hot when they want a shower.
Moving water heating into the surplus window is usually the single largest gain available on an existing system, and it requires no new storage.
Other flexible loads
Pool pumps, borehole and irrigation pumping, dehumidifiers and vehicle charging are all deferrable in the same way. The common feature is that the timing is negotiable.
Loads that are not negotiable, such as lighting and refrigeration, are not candidates. There is nothing to schedule.
How the control logic decides
The logic watches available generation and state of charge. When there is surplus and the battery is comfortable, it brings a flexible load on. When generation drops or the battery falls below a threshold, it drops the load again.
We run this at our own Langebaan office on the water heating, which is where it was tested before we proposed it to anyone else.