Withdrawal and injection at mixed sites explained

Infographic of the net flow at the electricity meter of a mixed site: consumption, solar panels and battery, with the withdrawal and injection cases

Withdrawal and injection explained for mixed sites combining consumption, solar panels and a battery

A consuming site equipped with solar panels and a battery does not just consume or produce: in reality, it withdraws or it injects.

The difference matters: what the power grid sees is neither the site’s gross consumption nor the panels’ gross generation, but the net flow measured at the electricity meter.

When the site withdraws, electricity flows from the grid to the site.
When the site injects, electricity flows from the site to the grid.

At any given moment, this net flow depends on four elements:

consumption + battery charging − battery discharging − solar generation

If the result is positive, the site is withdrawing.
If it is negative, the site is injecting.

For example, if a site consumes 5 kW, its battery charges at 3 kW and its panels produce 6 kW, the meter will see a net withdrawal of 2 kW.

It is this net power, whether withdrawn or injected, that must be controlled and monetised on flexibility mechanisms.

The virtual power plant (VPP) we are building at Nexen GridTech controls behind-the-meter batteries while taking account of the site’s physical reality, its economic logic and the regulatory constraints needed to turn this flexibility potential into revenue.

Do you distribute or install batteries? Get in touch to explore flexibility control as an alternative to a feed-in tariff for surplus solar.