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Setting export and generation limits

Short answer

An export limit caps net power to the grid at the meter, enforced by a G100 scheme with a grid CT. A generation limit caps the inverters' total AC output (Registered Capacity) in protected settings. DNOs may impose either. With a 5 kW export cap, an 11 kW inverter can still supply the home at up to 11 kW.

Last checked 24 September 2026 · 6 sources

What should I know before deciding?

Export limit breaches are prevented by G100 fail-safe on CT loss. Generation limit reduces what G98/G99 counts; changing it needs DNO notification (G99 20.3.2). Some installer sites wrongly define 'generation limit' as array size.

What does G100 require of an export limitation scheme?

The scheme must keep export at the connection point within the agreed limit, use a fully type-tested scheme or submit test evidence before commissioning, protect settings from the owner, and fail safe. If the grid CT, meter or communications are lost, output must fall to the limit or shut down. MIS 3012 requires CT faults or removal to be detected.

GivEnergy declaration: meter/CT at grid supply, one reading per second, limit within 5 s, fail-safe on comms loss. Fox H1 G2: soft limit within 15 s, hard trip if soft limit fails or CT/meter comms lost.

Can an inverter's rating be raised in software later?

Sometimes. G98 and G99 let manufacturers limit Registered Capacity in software if the customer cannot change it. Powerwall 3 is configurable from 3.68 to 11.04 kW. But raising it later changes Registered Capacity: G99 requires the DNO to be notified before the change, and going above 16 A per phase needs a new G99 application.

A 20% or greater capacity increase counts as significant modification (G99 20.3.6). Record the configured rating and firmware at commissioning. Hardware that is physically 3.68 kW cannot be raised.

How do I set an export or generation limit on a Tesla Powerwall 3?

In Tesla One, go to Settings > Import & Export Limits and set the Site Export Limit in watts, with export permission 'Solar Only' or 'Solar and Battery'. The system reduces battery discharge, then charges, then curtails solar. The inverter power rating (3.68-11.04 kW) is set separately at commissioning to match the DNO-agreed Registered Capacity.

Limits act at the site meter, which can be a virtual aggregated meter. Record both settings for the DNO and handover.

How do I set an export or generation limit on a Fox ESS hybrid (H1/AC1 G2)?

On the inverter go to Settings (default password 0000), then On-Grid Parm, then Export Control, and enter the limit in watts. A CT or DDSU666/SDM230 meter on the grid-side live must be fitted with the arrow toward the grid. The soft limit acts within 15 s; if that fails or CT or meter comms are lost, the inverter trips.

Wrong CT orientation defeats anti-backflow. Fox Evo/KH use FoxCloud/app equivalents - check model manual.

What to do next

Record the design assumptions, protection settings and commissioning results. Keep the DNO approval and final settings with the handover pack.

Sources

Last checked: 24 September 2026