Hi Martin

By default, a PV system will feed the house as a primary, and export as a secondary. I’ve never heard of anyone feeding out only, and not sure how you would go about this as it feeds into the mains board?

If your worried about power cuts, I can only recommend a Tesla battery as back up, as they are built for the American market, were power cuts are more usual, due to the nature of their cobbled together grid system.

The battery installer can then check your existing set-up for faults too.

Hope this help.

Stuart.