Why is a small amount of my electricity exporting back to the grid?

Sometimes exported energy to the grid from either the battery, inverter or solar panels can occur. At these times you may expect to be consuming all of the energy. This is a normal phenomenon and is explained in the article below.

Exported Energy

Looking at the diagram above, the home is consuming an energy level of 1.57kW.
From the battery (1.02kW) and solar generation (0.57kW) and there appears to be a small amount of leakage back to the grid (0.0274kW).

For some context of how these figures fit together: the system generation aka solar + battery, 0.57 + 1.02 = 1.59kW in total. The total minus the consumption, 1.59 - 1.57 = 0.02kW i.e. the leakage. The battery and solar are outputting more than the home is consuming so you have some exported back to the grid.

The reason this sometimes happens is because we cannot stop electricity flowing, it simply follows the path of least resistance. The battery is a reactive system, it cannot predict the future (as much as we try!).

Quick example;

If you put the toaster on, the home load will increase and the inverter will see this and tell the battery to start discharging. This is not an immediate process as the inverter has to convert the DC electricity stored in the battery to usable AC electricity in the home, so there is a small period where the home will pull from the grid to power the toaster until the battery takes over.

It works the same when the toaster is finished, the battery will still be discharging and in the space between the toaster finish and the inverter telling the battery to stop, the energy will flow back to the grid.

Similar scenarios can happen when the solar suddenly starts generating a lot more energy due to the sun coming through the clouds, it may take a short amount of time to wake the battery to begin charging so export will happen naturally.

The system constantly tries to find a balance but cannot predict the random nature of a home, so sometimes small amounts get exported back to the grid.

This being said, 0.0274kW back to the grid is very small and if this was maintained for an hour it would equate to 0.11 pence (using a base SEG of 4.1p per kWh).

In terms of energy lost for consumption; if you were to import that amount of energy from the grid for an hour it would equate to a 0.78 pence total cost (using Ofgem energy price cap 2024 of 28.62 pence per kWh). The total cost would equate to 0.67 pence overall taking away the money gained from exporting the energy.

The total cost is low but even so, this type of situation is unlikely to occur and the majority of times it does not occur for more than 5-10 minutes.