Do I need a zero-export device?

We believe zero export only makes sense in combination with a battery, to optimize for self-consumption.

A zero-export device stops your plug-in solar system from sending surplus electricity to the grid. That surplus arises whenever the panels out-produce whatever the house is drawing at that moment. Without a battery, the only way to stop that surplus leaving is to stop generating it, so the device throttles the panels back. You do not save more; you simply produce less.

With a battery in the system, the same device becomes useful, because the surplus has somewhere to go and can be used later instead of given away.

There is a practical cost too. Zero export needs a power meter installed in your breaker panel by an electrician, with current transformers watching both legs of your service so the controller knows what the whole house is doing.

Why would anyone want to stop exporting?

"Backfeeding" is frequently used with a negative connotation in the public discourse around solar. We observe two completely separate things being conflated by utilities opposing plug-in solar for commercial reasons and by vendors of zero-export systems: (1) backfeeding during a grid outage, which would indeed be dangerous. No plug-in solar system does that. (2) backfeeding during normal operation, which is not harmful or undesirable in any way. It's simply gifting a bit of energy back to your utility. The only reason why you would want to prevent backfeeding during normal operation is "flying under the radar" of the interconnection rules in states that don't yet have laws exempting plug-in solar form those rules.

Does the kit prevent backfeeding during normal operation out of the box?

No. A standard plug-in kit consisting of only a microinverter and solar panel has no way to know what the rest of your house is consuming, so it cannot decide when to throttle. That awareness has to be added through a power meter (often referred to as CT Monitor) that gets installed in your breaker panel.

How do I minimize backfeeding if I want to?

Sizing the system to your daytime load is the cheaper answer than engineering the export away. Match generation to the power you continuously use during daylight hours.

This came out of a lively back-and-forth among members in the Bright Saver Community, several of whom had priced the hardware before deciding against it.