Distribution Feeder Hosting Capacity

A distribution feeder's rooftop-solar hosting capacity is the amount of solar generation it can accommodate without compromising electricity quality, equipment ratings or protection. It is determined for specified connection locations and operating conditions, usually with existing equipment and controls, rather than as a universal percentage of feeder demand or transformer capacity.

Build a feeder-specific model

The assessment begins with an electrical model of the feeder and the distribution transformers supplying consumers. Both the amount and location of solar matter because electricity flows through different network sections before reaching other consumers or the upstream grid.

• The model includes network topology, conductor impedances, equipment ratings, phase connections and existing voltage-control devices.
• Engineers use time-varying demand and solar generation to represent their coincidence, including high solar output during low daytime demand.
• Existing solar installations and proposed connection locations are included; uneven connections across phases can produce different results from an evenly distributed installation.

Increase solar capacity until a technical limit is reached

Engineers progressively increase simulated solar capacity and check network performance. For each assumed deployment pattern, the first binding technical constraint establishes the hosting limit under the assessed conditions.

• Voltage limits are checked throughout the feeder: local generation can raise voltage, particularly where network impedance is high.
• Thermal ratings of conductors and transformers must remain satisfied under the resulting power flows.
• Protection coordination must remain effective so that faults are detected and isolated correctly; distributed generation can alter fault currents and their direction.
• The assessment also checks power quality, phase imbalance and voltage-control operation where relevant.
• Reverse power flow is not automatically unsafe; its acceptability depends on equipment capability, voltage control and protection arrangements.

Validate the limit and assess ways to increase it

A single snapshot or total installed capacity is insufficient to establish a reliable limit. Time-series power-flow analysis can reveal violations caused by changing demand, solar output and control-device operation.

• Different connection locations and credible operating scenarios are tested, with suitable allowance for uncertainty in demand, generation and network data.
• The usable capacity is constrained by the most restrictive applicable limit across the assessed scenarios; results may therefore be location-specific rather than one feeder-wide number.
• Smart-inverter voltage support, phase balancing, network reinforcement, storage or controlled export can increase hosting capacity, but their effectiveness must be reassessed in the feeder model.
• An export limit must be distinguished from installed panel capacity because self-consumption, storage or curtailment can reduce injection into the grid.