The core problem
Why is a battery essential under NEM 3.0?
NEM 3.0 — officially the Net Billing Tariff — pays you $0.05–$0.08 per kWh for solar power you export to the grid. But from 4–9 PM, when your panels are winding down and your home is ramping up, SDG&E charges $0.55–$0.70 per kWh. That 10x spread is the whole game: every kilowatt-hour you can shift from midday production to evening consumption is worth roughly ten times what the grid pays you for it.
A battery does exactly that shift, automatically, every day. It charges from your panels through the afternoon and powers your home through the peak window. That's why solar-only systems in SDG&E territory now capture only ~70% of the savings a solar + battery system does.
2026 economics
What does a battery cost — and what do the rebates cover?
| Item | Amount | Notes |
|---|---|---|
| 13.5 kWh battery installed | $10,000–$15,000 | Powerwall 3 or equivalent, added at time of solar install |
| SDCP upfront rebate | −$250–500/kWh (up to $6,750) | SDCP customers in SDG&E territory · funds limited |
| SDCP performance payments | ~$250/yr | $0.10/kWh for evening discharge participation |
| SGIP RSSE (income-qualified) | up to $1,100/kWh | CARE/FERA or ≤80% AMI · waitlisted · apply pre-install |
| SGIP general-market rebate | CLOSED | Ended December 30, 2025 |
| Federal 30% credit | EXPIRED | Ended December 31, 2025 for homeowner purchases |
Bottom line
What it does to payback
| Configuration | Typical payback | 25-yr net savings |
|---|---|---|
| Solar only (cash) | 9–10 years | ~$62K–77K |
| Solar + battery (no rebate) | ~10 years | ~$95K–118K |
| Solar + battery (SDCP rebate) | 7–8 years | ~$95K–118K, faster break-even |
For SDCP customers, the rebate effectively erases the payback penalty of adding storage while keeping all the additional savings — which is why we recommend solar + battery as the default configuration in SDG&E territory, and why installers who can't speak fluently about SDCP enrollment are scored down in our 14-signal evaluation.