Does a JADU need its own electrical panel or meter?

Generally no. A junior ADU (JADU) is a unit of no more than 500 square feet of interior livable space contained entirely within a single-family home, and state law says it is not considered a separate or new dwelling unit for purposes of water, sewer or power service. In practice a JADU typically runs off the home's existing service and meter, and whether it gets new circuits or a small subpanel depends on the load calculation and the scope of work.

What state law says

• Definition. A JADU is no more than 500 square feet and sits within the walls of a proposed or existing single-family residence, which can include an attached garage (Gov. Code, § 66333).
• Utility service. For water, sewer or power service, including connection fees, a JADU is not treated as a separate or new dwelling unit (Gov. Code, § 66338). A local agency can still adopt a service or connection fee rule that applies to single-family homes containing a JADU.
• Separate connections. HCD's ADU Handbook explains that ADUs and JADUs created from existing space under Gov. Code § 66323(a)(1) cannot be required to install a new or separate utility connection unless they are built at the same time as a new single-family home (Gov. Code, § 66311.5).

The efficiency kitchen

HCD's handbook says a local agency can't require specified electrical or gas connections or appliance types for a JADU's efficiency kitchen, and it notes that 220-volt circuits are not required. If you choose to install a 240-volt cooktop or range, it still needs a properly sized dedicated circuit and a line in the load calculation.

What the electrical code still requires

• New and extended circuits follow the current California Electrical Code, including GFCI protection at countertops and other required locations.
• When branch circuits serving areas such as kitchens, bedrooms and living spaces are modified, replaced or extended, Section 210.12(E) requires AFCI protection for that circuit, with a narrow exception for short extensions that add no outlets.
• Smoke and carbon monoxide alarm requirements for the home still apply.
• The home's existing service must be able to carry the added load, which the load calculation confirms.

When a subpanel makes sense

A subpanel is a design choice, not a state requirement. It can make sense when a JADU in a converted attached garage gets a new kitchen, bathroom and heat pump circuits and the main panel is out of breaker spaces. It still sits on the same service and meter as the house.

What this means for your electrical plan

The plan should show the existing panel and service rating, a load calculation that includes the JADU's new loads, each new or extended circuit with its GFCI and AFCI protection, and any subpanel. See AFCI requirements, reusing existing garage electrical and why load calculations matter.

Sources: hcd.ca.gov, california.public.law, dgs.ca.gov.