If you got solar quotes in San Diego recently, almost every one probably included a battery — and you may have wondered whether that's an upsell or a real necessity. Under the old rules, a battery was optional. Under NEM 3.0, it's the single biggest factor in whether your solar system actually saves you money. Here's the honest breakdown.
Why Batteries Matter So Much More Under NEM 3.0
The whole math of solar changed when California moved from NEM 2.0 to NEM 3.0 (the "net billing tariff"). The short version:
- Under NEM 2.0, SDG&E paid you nearly retail rate for every extra kilowatt-hour your panels sent back to the grid. Your house was basically a free battery — push power out at noon, pull it back at night, roughly even.
- Under NEM 3.0, the credit for exported power dropped by about 75%. Sending solar to the grid now earns you only a few cents per kWh, while buying it back in the evening can cost 45¢ or more.
That gap is the problem. Your panels make the most power in the early afternoon, but San Diego homes use the most power from 4-9pm — exactly when SDG&E rates peak and solar production is fading. Without somewhere to store your cheap midday solar, you're forced to sell low and buy high.
A battery closes that gap. It soaks up your excess midday production and discharges it during the expensive evening peak, so you're using your own stored solar instead of buying SDG&E's most expensive power.
What a Battery Actually Does for Your Bill
Think of it in three jobs:
- Peak shaving. The battery covers your 4-9pm usage so you avoid SDG&E's highest time-of-use rates. This is where most of the savings come from under NEM 3.0.
- Self-consumption. Instead of exporting cheap and importing expensive, you consume nearly all the solar you produce. More of every panel-hour stays in your pocket.
- Backup power. When the grid goes down — wildfire-season Public Safety Power Shutoffs (PSPS), storms, rolling outages — your essentials keep running. Solar alone shuts off in an outage for safety; only a battery keeps the lights on.
How Much Does a Battery Add to the Cost?
A single home battery (think 10-13 kWh of usable capacity) typically adds $8,000-$15,000 to a cash purchase before incentives, depending on brand and how many you need. Larger homes or whole-home backup may need two.
But two things soften that:
- The 30% federal tax credit applies to batteries too — including batteries added to an existing solar system, as long as they're charged primarily by solar. That knocks several thousand off the real cost.
- On a $0-down PPA, you don't pay for the battery upfront at all. You pay a fixed per-kWh rate for the power the system produces and stores — typically 18-22¢/kWh versus SDG&E's 45¢+ — so the battery is baked into a monthly figure that's still below your utility bill.
| NEM 2.0 (old) | NEM 3.0 (today) | |
|---|---|---|
| Export credit | ~retail rate | ~25% of retail |
| Battery needed for good ROI? | Optional | Strongly recommended |
| Best strategy | Oversize panels | Right-size panels + battery |
| Evening peak coverage | Grid credits | Stored solar |
When a Battery Is — and Isn't — Worth It
A battery makes the most sense if you:
- Have high evening usage (EV charging, AC, a full house home after 4pm)
- Are on a steep time-of-use plan with SDG&E
- Want backup through PSPS and outage season
- Are buying or financing the system and can use the 30% tax credit
It matters less if your usage is genuinely tiny, or if you're rarely home in the evenings — but in San Diego, with SDG&E's rate structure, those cases are rare. For most homeowners here, solar without storage under NEM 3.0 leaves a lot of savings on the table.
The Bottom Line for San Diego Homeowners
NEM 3.0 didn't kill solar — it changed the winning strategy. The old play was "make as much power as possible and sell the extra." The new play is "make what you use and store it for the evening." A right-sized system with a battery, especially on a $0-down PPA where the storage is included in the rate, is how San Diego homeowners still beat SDG&E.
The right size depends on your actual usage, roof, and rate plan — which is exactly what a free consultation sorts out.
Find Out If a Battery Makes Sense for Your Home
Use our calculator with your real SDG&E bill, then book a free consultation for a personalized assessment.
Free Solar Consultations helps San Diego homeowners understand their options under NEM 3.0 and connect with trusted solar providers. We serve the entire SDG&E service territory. Call (619) 396-7530 or book your free consultation online.