Solar (C-46) · Lesson 5 of 6

Home Battery Systems: BESS-Ready Panels and Where Batteries May Go

"Home Battery Systems: BESS-Ready Panels and Where Batteries May Go" is lesson 5 of 6 in the Solar (C-46) Learning Hub. It opens with "The BESS-Ready Rule for New Homes" and works through 5 short steps, then a worked example you can check yourself against.

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Steps in this lesson

  1. The BESS-Ready Rule for New Homes
  2. The Four Backed-Up Circuits, the Busbar and the Transfer Switch Space
  3. Where a Residential Battery May Be Installed
  4. Size Limits: 20 kWh Per Unit, 600 kWh Per Property, and Table R330.5
  5. Spacing, Alarms and Vehicle Impact

The worked example in the course applies this lesson to a realistic job in 5 steps, from "Check each unit against the individual limit" through "Find the spacing run".

What you'll be able to do

  • Explain the main idea of "Home Battery Systems: BESS-Ready Panels and Where Batteries May Go" in plain language you can use on the exam.
  • Apply this step with confidence: "Where a Residential Battery May Be Installed".
  • Apply this step with confidence: "Size Limits: 20 kWh Per Unit, 600 kWh Per Property, and Table R330.5".
  • Apply this step with confidence: "Spacing, Alarms and Vehicle Impact".
  • Test yourself on the worked example and the quick-check quiz inside the classroom.
Home Battery Siting: CRC R330ATTACHED GARAGE, BACK WALL (plan view)13.5kWh13.5kWh13.5kWh3 ft3 ftWall run = 3 x 2 ft + 2 x 3 ft = 12 ft3 units x 13.5 kWh = 40.5 kWh totalTABLE R330.5 AGGREGATE LIMITSUtility closet / basement40 kWhAttached garage80 kWhExterior wall (within 3 ft)100 kWhEach unit max 20 kWh; property max 600 kWhEach unit: 13.5 is under 20 kWhOKCloset: 40.5 is over 40 kWhFAILSGarage: 40.5 is under 80 kWhOKUnits at least 3 ft apart (R330.3.1)Install in the attached garage on 12 ft of wall, not in the closetNever in a sleeping room or a closet opening directly into one (R330.4)Source: 2025 California Residential Code R330.3.1, R330.4, R330.5, Table R330.5 (CFC 1207.11 matches for R-3)CC
The diagram for this lesson, exactly as it appears in the Learning Hub.

The first steps of this lesson

Step 1: The BESS-Ready Rule for New Homes

2025 California Energy Code Section 150.0(s) applies to single-family residences with one or two dwelling units where the utility service is greater than 125 amps. Unless a BESS is already installed (the exception), the home must have either BESS-ready interconnection equipment with at least 60 amps of backed-up capacity and at least four BESS-supplied branch circuits, or a dedicated raceway of trade size not less than 1 inch from the main service to a subpanel that supplies those circuits. That subpanel must be labeled "Subpanel shall include all backed-up load circuits."

Step 2: The Four Backed-Up Circuits, the Busbar and the Transfer Switch Space

Section 150.0(s)2 requires at least four branch circuits identified and collocated at a single panelboard suitable to be supplied by the BESS: at least one for the refrigerator, one lighting circuit near the primary egress, and at least one sleeping room receptacle outlet. Section 150.0(s)3 requires the main panelboard to have a minimum busbar rating of 225 amps. Section 150.0(s)4 requires space reserved for system isolation equipment or a transfer switch within 3 feet of the main panelboard, with raceways installed between the panelboard and that location.

The remaining 3 steps, the worked example and the quiz are in the course. This is a preview. The full lesson, with the step-by-step explanations, a worked example and a quick-check quiz, is inside the classroom.

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