What the backup load panel does and why it matters.

The backup load panel (critical load sub-panel) is the electrical component that separates your backed-up circuits from the rest of your home. Without it, essential-load battery backup is not possible.

• →Circuit separation. Selected circuits — refrigerator, key lighting, internet, medical devices, select outlets — are moved from your main panel to the sub-panel. During a grid outage, battery power flows to the sub-panel. Everything on the main panel loses power. This is intentional: limiting backed-up load extends how long the battery can sustain those circuits.
• →Sub-panel sizing. The sub-panel must be sized to handle the total amperage of your backed-up circuits with appropriate breaker space. We size and specify the sub-panel based on your backup circuit list and battery capacity during the estimate.
• →Location and installation. The sub-panel is typically installed adjacent to the main panel. Circuit breakers for backed-up circuits are physically relocated to the sub-panel. All work is done to code and permitted through LADBS or the applicable local jurisdiction.
• →Whole-home backup exception. If you are configuring whole-home backup with a compatible Tesla Powerwall 3 installation and main panel, a separate sub-panel may not be required — the Powerwall 3 architecture can back up the entire main panel. We confirm the right configuration for your home during the estimate.

Tesla Backup Gateway & Powerwall 3 architecture.

The Backup Gateway is the control and transfer hub for Tesla Powerwall installations. Powerwall 3 integrates this functionality directly into a unified architecture. Either way, the Gateway function is what makes automatic transfer work.

• →Grid monitoring. The Gateway continuously monitors the grid connection. When it detects a power failure, it switches the home (or backed-up circuits) to battery power within milliseconds — fast enough that most electronics and appliances stay running without restarting.
• →Island mode (backup mode). When the grid is down, the Gateway isolates your home from the grid and operates the battery in island mode, allowing solar (if present) to continue charging the battery safely. This is what allows solar-extended backup during daytime outages.
• →Charge source management. The Gateway manages how the battery charges: from solar panels, from the grid during off-peak hours (in time-of-use configurations), or both. Configuration is managed via the Tesla app.
• →Backup reserve setting. You can reserve a percentage of battery capacity exclusively for grid outages (typically 20–100%), regardless of how the battery is used for time-of-use optimization during normal operation. We help configure this to match your priorities during commissioning.

Enphase IQ System Controller & battery integration.

Enphase battery installations use the IQ System Controller (or IQ Combiner with Envoy) to manage automatic transfer and backup operation. The principle is the same: when the grid fails, the system isolates backed-up circuits and powers them from the Enphase IQ Battery 5P units. The Enphase Installer Toolkit and Enlighten portal manage configuration and monitoring. We specify the complete Enphase integration — IQ System Controller, battery modules, and sub-panel — as part of every Enphase backup installation.

Enphase battery installation guide →

What we check before specifying your electrical scope.

• →Main panel age and capacity. Older panels or those with limited breaker space may need upgrades to accommodate battery system components. We assess breaker space, bus bar rating, and service size.
• →Grounding and bonding. Battery backup systems require proper grounding and bonding. We verify compliance during the electrical assessment.
• →Solar interconnection point. If solar is part of the system, we confirm the interconnection point between solar inverter, battery, and Gateway for proper AC or DC coupling.
• →Location for Gateway and battery. We identify wall space for the Gateway (typically near the panels) and a suitable location for the Powerwall or Enphase units: garage wall, utility room, or exterior (where code-compliant).

What to review before your load panel and Gateway estimate.

• →Main panel photos: include the panel door label, breakers, service rating, meter area, and nearby wall space.
• →Backed-up circuits: identify refrigerator, lighting, internet, medical equipment, garage opener, mini-split, or other priority loads.
• →Solar and utility details: note existing inverter model, solar PTO status, utility account, and whether the system is LADWP or SCE.
• →Future upgrades: mention EV charging, heat pump plans, panel upgrade needs, or later battery expansion.

Useful next pages: essential-load backup, whole-home backup, battery sizing, and permits and inspections.

Explore the battery cluster.

Solar, roofing & battery together.

Backup load panel & Gateway questions.