What do you mean by 'surplus solar'?
The plan does not store your solar, it simply monitors what your solar panels are producing. When your solar is making enough energy to power your home and also some extra, that would then go into the grid, the Voltello devices kick in and automatically adjust your air cons to use this 'extra' power. This means that all the free power being produced by your solar panels is being used by your home. Think of it this way, your home energy use can go up and down, so does the energy your panels are producing depending on how much sun there is. The 'Surplus Solar for Comfort' plan adjusts your home energy use to match the energy your solar panels are producing. So, when there is extra energy that you would be exporting to the grid, you heating or cooling is increased slightly to use the energy. We call this a 'solar following' algorithm. If your solar panels are not producing much energy, say if it is cloudy, your air con will still run if you want it to, it will just mean you will probably be using grid energy.