G100 export limitation: batteries on a constrained grid

“Our grid connection is already constrained, so we probably can’t add a battery.” It is a common assumption, and it is often the opposite of the truth. On a constrained connection, the battery can be part of the solution rather than the casualty, and the tool that makes it work is a G100 limitation scheme.

The problem: a constrained connection

Many UK commercial sites are close to the limit of their agreed import capacity, especially in busy industrial areas. When a business wants to add load (EV charging, a heat pump, more production), the DNO’s answer can be a network reinforcement with a significant cost and a long wait. That is enough to stop a lot of good projects.

What G100 does

G100 is an export (and import) limitation scheme. It continuously monitors the site’s power flow and automatically curtails the controllable assets (the battery, and sometimes chargers or generation) to keep the whole site within its agreed import and export capacity. It has to respond within the limits the G100 recommendation sets, so that the site stays within its agreement even as loads swing.

The practical effect can be significant: because the DNO can rely on the scheme to hold the site within capacity, a battery (and sometimes new load behind it) can be connected without the reinforcement, if the DNO accepts the scheme. The battery charges off-peak or from on-site solar, then discharges to buffer peaks, so the connection sees a smoothed load rather than the raw spikes.

Where it changes the answer

• EV charging hubs. Rapid and ultra-rapid chargers create severe demand spikes. A battery with G100 can buffer those spikes so more chargers fit on the existing connection, which can cost less than a reinforcement. See the EV-charging storage guide.
• Adding production load. A manufacturer wanting more capacity may be able to use a containerised battery with G100 to add load inside the existing agreement.
• Solar-plus-storage. A retrofit uses G100 export limitation to stay within the agreed export capacity while keeping more generation on site.

What an installer should do

G100 is not a box you buy; it is a scheme that has to be designed and proved. The installer should design the limitation and its protection, agree the approach with the DNO before final design, and demonstrate the function at commissioning so that both you and the DNO can see it holding the site within its limits (see what battery storage commissioning covers). Ask whether the DNO has accepted the proposed scheme before you commit to plant.

Next step

If your connection is tight and you have been told a battery or new load is off the table, it may not be. Request installer quotes and ask each installer whether a G100 scheme would work on your connection; your enquiry is passed to installers who cover your area, and this site is not one of them. For a wider view, read whether commercial battery storage is worth it.