How is solar handled on electrical plans for an ADU?

Solar shows up on ADU electrical plans in one of three ways: a full solar PV system, solar-ready conduit and panel provisions, or — increasingly — solar paired with battery storage (ESS-ready). For qualifying newly constructed detached ADUs, the California Energy Code may require solar PV (or, where not required, solar-ready conduit), and the electrical set has to show how the system connects to the panel.

What gets shown on the plans

When solar applies to your project, the electrical plans coordinate the following so plan check and the installer have a complete picture:

• The PV interconnection point — whether the solar ties in at the ADU subpanel, a dedicated solar disconnect, or the main service — and the conductor routing.
• Conduit pathways from the roof/array location down to the point of connection.
• Panel space and labeling — a reserved breaker and the required PV system signage/labeling.
• The load side vs. supply side connection method and any back-feed breaker sizing per code (the 120% busbar rule where applicable).
• Where solar isn't installed but the unit must be solar-ready, the reserved conduit, roof area, and panel space documented so a future system is a simple add.

Solar and battery storage often travel together

ESS-ready (Energy Storage System-ready) provisions frequently accompany solar, because batteries and PV are designed to work together. Where the energy code requires it, the plans coordinate:

1. Solar PV interconnection point and conductor routing.
2. A backup/emergency subpanel and its backed-up circuits.
3. Conduit pathways for both the PV system and a future battery.
4. Panel space and labeling for all of the above.

Which ADUs need solar

This is squarely a verify-for-your-project item. Applicability depends on whether the ADU is newly constructed and detached, the conditioned floor area, the climate zone, and the energy-code version in effect — and local jurisdictions can layer additional requirements. Garage conversions and attached additions often follow different rules than ground-up detached units, and may be exempt from the solar mandate.

Requirements vary by jurisdiction and energy-code cycle — confirm what solar and ESS-ready provisions apply to your specific project with your local building department.

When these provisions apply, they must appear on the electrical plans; our electrical plan sets incorporate the PV interconnection, conduit, and any backup panel, and our Title 24 reports document the energy-code basis. See the complete MEP guide for how solar, storage, and panel design fit together.