Adding an accessory dwelling unit in Chula Vista creates a practical solar-and-battery question: will the proposed backup system serve the ADU as well as the main house? It can be a useful goal for the project, but the answer depends on the approved electrical design and the circuits included in the battery proposal.
For a Chula Vista property served by SDG&E, bring the ADU plans into the solar discussion before accepting a quote based only on the existing house.
Start with the meter and panel plan
Chula Vista's ADU guidance says an ADU may have a separate electric meter and address. That does not settle the arrangement for your property; confirm it with your designer, the city and SDG&E. The city's ADU resource page is a useful starting point.
Ask the electrical designer to identify the meter serving each dwelling, its electrical panel, and the circuits proposed for backup. Then have the battery installer mark exactly which ADU loads would remain powered during an outage. A battery located on the same lot is not, by itself, confirmation that both dwellings are covered.
If separate meters are proposed, request a design and utility review specific to that arrangement. Do not assume solar production, bill credits or backup power automatically transfer between accounts.
Include the ADU's future electricity use
An existing utility bill cannot show electricity use from an ADU that has not been occupied yet. Give the project team the planned appliance list, heating and cooling equipment, water heater, cooking equipment and expected occupancy. Label estimated future use separately from the main home's measured consumption.
SDG&E's My Project Center covers projects including ADUs and solar installations. Its service-request guidance calls for a project scope, site plans and load calculations. Coordinate that work with the ADU designer and solar installer so their proposals describe the same finished property.
Annual solar sizing is also different from outage coverage. Our explanation of 100% solar offset shows why an annual energy match does not mean every hour is supplied by solar.
Choose an outage plan for both dwellings
Make two lists: essential loads in the main house and essential loads in the ADU. Refrigeration, selected lights and communications may be priorities; electric cooking, water heating and cooling need their own equipment review.
As general battery guidance, PG&E explains that only backed-up circuits receive power, and larger loads can shorten backup time or exceed system capability. Those design questions also matter when evaluating an SDG&E property.
Ask for an estimate using both dwellings' selected loads together, with stated assumptions about starting charge and solar recharge. Storage is finite, and solar can replenish it only when sunlight and compatible backup equipment permit. Have the installer demonstrate the agreed coverage at handover.
Put the ADU scope into the PPA
A qualifying solar-plus-battery PPA may help avoid an upfront equipment purchase while supporting the planned property. Under a PPA, the provider owns the solar system and charges for its generated electricity, as the CPUC consumer guide explains.
Request written terms covering the battery, served dwelling or dwellings, electrical upgrades, installation charges, ongoing payments, rate or escalator, contract length, maintenance and transfer provisions. If the ADU will be added later, ask how expansion would affect equipment and payments. No-upfront eligibility depends on the offer; utility charges can remain and savings are not guaranteed.
Bring your ADU plans and current electric bills to the West Coast Alternatives consultation process to explore a proposal built around the complete property.