Now that you have installed Solar PV the point at which your OWL Transmitter & Sensor is installed (normally on live cable between your meter and consumer unit) will now have electricity flowing through it in both directions. The Sensor is unable to tell which direction the electricity is flowing and thus it is all seen as consumption, hence your higher values.
Depending upon your wiring configuration you may be able to relocate the Sensor to a cable which does not have the Solar PV generated energy flowing through it.
We recommend that you consider our OWL Intuition-pv product. This is an Internet connected system that has been specifically developed for homes with Solar PV installed. Further details can be found here.