Many solar customers have a separate rate at which their utility provider purchases their excess solar production. You can set this separate rate in the Sense app.
On both the web and mobile apps, tap the gear icon in the top-right corner of the Solar screen.
It is important to note that this section of Sense app is not currently localized for regions outside of the US & Canada. You may not be able to set the Sense to reflect local currencies, billing rates, or terms.