A solar-plus-battery proposal may show “100% offset” beside its production estimate. For an SDG&E homeowner, that can be a useful starting point for understanding system size. It is not, by itself, a promise of a zero utility bill or a particular saving.
A qualifying no-upfront PPA can help you access renewable generation and storage while preserving cash. To evaluate the offer, ask how its energy percentage connects to your actual household budget. Official sources were checked September 16, 2026.
Ask what the percentage measures
Have the provider write out the calculation, including the period and usage baseline. If the proposal defines offset as estimated annual solar production divided by annual household electricity use, a system forecast to generate 8,000 kWh against 8,000 kWh of use shows 100%.
That is an illustrative calculation, not an SDG&E billing rule or a production guarantee. Confirm whether the denominator uses historical consumption or a forecast that adds an EV, heat pump or other planned load. Check whether battery losses are included in the model.
The annual ratio does not tell you how much solar is used directly, how much enters storage or how much is exported. Ask for those figures separately.
Equal annual energy can still involve grid purchases
Consider a simplified example without a battery or storage losses. Assume a home uses 8,000 kWh over a year and its solar system generates the same amount. If it uses 3,000 kWh of that solar directly, it exports the remaining 5,000 kWh and imports 5,000 kWh at other times.
Annual generation matches annual consumption, but the household still exchanges substantial electricity with the grid. These invented energy totals do not establish a dollar bill; the timing and applicable prices are missing.
SDG&E’s Solar Billing Plan overview explains that import prices and export credits depend on time, with exports valued by hour. Residential Solar Billing Plan customers use EVTOU5, and residential solar accounts also pay a Base Services Charge. Customers with a Community Choice Aggregator should confirm generation pricing with that provider.
Ask the proposal to use your actual tariff and generation provider. Earlier NEM arrangements require their own calculation. Our SDG&E monthly-billing and true-up guide explains the settlement calendar.
Show what the battery changes
SDG&E describes storing daytime solar for use during its 4–9 p.m. on-peak hours. Request a comparison with the proposed storage capacity, operating schedule and backup reserve included. The useful question is how storage changes purchases, exports and total costs, rather than whether it makes the annual offset label larger.
Keep outage performance separate. PG&E’s general battery guidance explains that supported circuits, available charge and connected demand determine backup duration. Those physical limits also matter in an SDG&E home. A 100% annual energy estimate does not establish whole-home backup or unlimited runtime; outage recharging needs suitable sunlight and compatible equipment.
Add the PPA payments to the remaining bill
Under a PPA, the provider owns the solar system and sells its generated electricity, as the CPUC’s consumer guide explains. Ask for a complete annual comparison showing provider payments, any separate battery charges, remaining utility costs and settlement effects without double-counting credits.
Confirm qualification for no upfront payment, installation charges, the rate, any escalator, term, battery ownership and inclusion, maintenance, replacement coverage and home-sale provisions. No upfront equipment purchase does not mean free electricity or guaranteed savings.
Bring the proposal’s offset calculation and your recent electricity history to West Coast Alternatives’ homeowner journey. A clear energy model and complete cost comparison make the potential benefits of solar and storage easier to evaluate.