A solar-plus-battery PPA can give an eligible SDG&E homeowner access to renewable generation and backup equipment through a qualifying no-upfront-cost offer. To understand its projected value, ask one question about the savings chart: how much does it assume utility electricity prices will rise?
That assumption can change a long-term forecast substantially. Seeing more than one scenario helps you judge the proposal alongside the equipment, service and backup capability you value.
Separate the two price schedules
The CPUC solar guide recommends asking what electricity-bill escalation assumption a savings estimate uses. It also explains that estimated savings are not guaranteed.
Keep two different figures on the proposal:
- The PPA's contractual electricity price and any scheduled escalator.
- The assumed future changes in utility prices used to forecast your bill.
The first describes what the agreement says about pricing. The second is a modeling assumption, not a promise from SDG&E. A known PPA price schedule can help with planning, but the invoice can still depend on billable generation and any separate charges.
See why the assumption matters
Consider a deliberately simplified illustration. Suppose a household's first-year electricity cost without solar is $2,400, usage stays unchanged, and the entire annual amount grows at one constant percentage. This is not an SDG&E rate forecast or a realistic tariff calculation.
After nine annual increases, in year ten:
- At an assumed 2% increase, the annual amount is about $2,868.
- At an assumed 5% increase, it is about $3,723.
The calculation is $2,400 multiplied by 1.02 or 1.05 nine times. The different assumptions create an approximately $855 gap in the modeled year-ten cost without solar. That gap is not solar savings: it excludes the PPA, remaining utility bill, battery charges and all other project costs.
Request the provider's standard forecast plus a clearly labeled lower-growth sensitivity case. Keep the same household usage and system assumptions so you can identify what changing utility prices alone does to the comparison.
Use the right SDG&E bill structure
A useful model needs more detail than increasing today's entire bill by one percentage. SDG&E's Solar Billing Plan information describes separate import charges and export credits, with export values varying by time and season. Residential solar customers also continue paying a Base Services Charge.
For customers served by San Diego Community Power or Clean Energy Alliance, that generation provider sets generation import and export pricing. Have the proposal identify your actual provider and applicable solar tariff; an existing NEM account needs its own treatment.
Ask which assumptions apply to imported electricity, fixed charges and exports. Do not assume all three grow together. Include the remaining utility costs in each scenario rather than comparing PPA payments alone with today's bill. Our SDG&E solar-offset guide explains why annual energy matching does not eliminate grid purchases.
Keep the battery comparison consistent
Use the same battery equipment, operating schedule and backup reserve across scenarios. PG&E's general storage guidance explains that reserve settings and household demand affect available backup energy. Those physical limits also apply to an SDG&E home.
Confirm supported circuits, battery ownership, service and replacement coverage. Outage duration depends on actual charge and loads; solar recharging needs suitable sunlight and compatible equipment.
Under a PPA, the provider owns the solar system and you make ongoing electricity payments. Review qualification, installation costs, the rate and escalator, term, separate battery fees, maintenance and home-sale transfer terms. No upfront purchase means neither free electricity nor guaranteed savings.
Bring the proposal's assumptions and your electricity history to the West Coast Alternatives homeowner journey for a comparison that makes both the potential benefits and ongoing payments understandable.