When comparing a solar-plus-battery PPA for an SDG&E home, ask whether the forecast accounts for electricity used by the battery system itself while it waits to charge or discharge. A clear answer helps you evaluate the complete system without adding the same loss twice.
This guide uses primary sources checked November 5, 2026. It does not assign a typical standby wattage to all batteries or promise a particular saving.
What does idle consumption mean in a model?
The System Advisor Model battery documentation distinguishes conversion losses from additional equipment consumption, such as temperature-control equipment. Its modeling options include losses while charging, discharging or idle; idle means neither charging nor discharging.
The documentation also says these additional losses default to zero, which is appropriate for most analyses. That is a modeling default, not a measurement of your proposed equipment. Ask the provider whether relevant consumption is already represented elsewhere and whether a separate allowance is warranted for the actual system.
Avoid copying an arbitrary standby number from another brand or adding a new penalty on top of an efficiency figure that already includes it. Request the equipment data and the explanation behind the forecast’s treatment.
Turn an assumption into a question
For a hypothetical example only, assume a separate auxiliary load averages 20 watts during 12 idle hours. That represents 0.24 kWh: 0.020 kW multiplied by 12 hours. It is not a manufacturer specification, an SDG&E household average or a prediction of energy taken directly from the battery cells.
Ask where that energy comes from in the modeled configuration and when it is consumed. Do not automatically multiply it by the highest electricity price or subtract it from every day’s available backup energy. Those steps require more information about operation and the energy pathway.
Our battery efficiency and PPA comparison guide explains the related question of energy measured before and after storage. Its PG&E example is illustrative; use your own utility arrangement for a quote.
Apply the actual SDG&E billing rules
SDG&E’s Solar Billing Plan guidance explains that import and export values depend on timing and highlights the 4–9 p.m. on-peak period. A community choice provider sets generation import charges and export credits for its customers. Confirm the provider and tariff on your statement rather than applying a generic bundled rate.
Request a comparison showing household consumption, battery operation, utility imports and exports, and PPA payments together. Existing NEM customers need their own billing rules modeled. A small equipment load is one input to that comparison, not a standalone verdict on whether storage is worthwhile.
Keep useful backup and ongoing costs visible
A qualifying no-upfront solar-plus-battery PPA can help eligible homeowners access equipment while preserving cash. The CPUC solar guide explains provider ownership and ongoing payments for solar electricity. Review the rate, escalator, term, battery charges, maintenance and transfer provisions alongside remaining utility costs. No upfront purchase does not mean free electricity or guaranteed savings.
For outages, general storage guidance explains why supported circuits, output limits, available charge and connected demand affect duration. Ordinary grid-tied solar alone generally does not provide outage power; compatible backup equipment and suitable sunlight are needed for solar replenishment. Do not disable battery controls or thermal management to reduce consumption.
Bring the proposed equipment model, forecast assumptions and utility bill to the West Coast Alternatives homeowner journey. Ask for a complete comparison that accounts for useful delivered energy and clearly states what is included in the offer.