Under net billing, the battery is the strategy.

Under net billing — yes, for almost everyone. Export credits were cut ~75%, so selling your excess solar to the grid is a losing trade most of the year. A battery stores your own daytime power for your own nighttime use, which is now the whole game. Without one, you'd need to size solar to only ~60-70% of usage and accept a permanent utility bill.

Batteries also unlock the stackable money: SDCP's $3,000-$6,000 rebate, VPP yearly payments, and those $1-$3.50/kWh August-September export credits. In 2026 California, the battery isn't the add-on. It's the strategy.

Net Metering (NEM) — still the rule in most states — lets you sell excess solar to the grid at retail rate. Produce more than you use across the year and your bill hits ~$0. Simple, forgiving, oversizing was smart.

Net Billing — California since 2023 — cut export credits by ~75%. Selling to the grid is now a bad trade for most hours of the year, which means the winning design changed completely: size solar to your daytime usage, add a battery to store your own power for nighttime, and minimize grid interaction. The twist: during August-September peak hours, SDG&E pays $1-$3.50/kWh for exports — so a well-designed battery system cashes in exactly when the grid is desperate. This is why systems designed after 2023 must be designed with software and your actual usage data (Green Button data), not napkin math. It's also why so many post-2023 systems from careless companies underperform.

Usually not — and some batteries provide no backup at all, by design. Three configurations:

• Grid-tied (no backup): replaces the grid at night for maximum savings, zero backup capability. Cheapest, and perfect if outages aren't your concern.
• Partial backup: the most common. Extra equipment backs up 2-10 essential circuits — fridge, lights, wifi. In a blackout, only those run.
• Whole-home backup: multiple batteries, most expensive, everything runs — until the batteries drain, so conservation still matters.

Modern systems "island" during outages: your solar recharges your batteries by day even while the grid is down. But sizing backup honestly — instead of letting a rep imply one battery runs your AC through a week-long outage — is the difference between a happy customer and a furious one.

Capacity (kWh) is how far a car can drive — the total energy stored. Power (kW) is the speed limit — how fast energy can flow out. A big battery with low power is a truck with a huge gas tank and a 25mph governor: lots of range, can't run the heavy stuff.

Heavy appliances — AC, pool pumps, EV chargers, dryers, heat pumps — need high power (generally 5kW+) just to switch on. They also drain capacity fast. This is why battery specs matter more than brand names: a Tesla Powerwall 3 (13.5kWh / 11.5kW) and an Enphase 5P (5kWh / 3.85kW) are built for completely different jobs, and both are excellent at their own job. Batteries stack like batteries in a remote — two 10kWh units = 20kWh — so systems are built from the load up.

Most batteries carry 10-year warranties; Enphase and Franklin stand out at 15. Nearly all guarantee ≥70% capacity at end of warranty. But the fine print has two traps:

Cycles: like a car's "5 years or 50,000 miles," some warranties cap full charge/discharge cycles (4,000-15,000). Daily-use batteries burn cycles fast — if you're cycling nightly (which is the whole point under net billing), a higher cycle limit or unlimited-cycle warranty matters enormously. Throughput: some cap total lifetime energy (e.g., 60MWh). Exceed either limit and the warranty is void even inside the time window. Backup-only batteries can ignore this; nightly-cycling batteries can't. This single paragraph has saved my clients more money than most sales pitches.

San Diego Community Power's battery program pays $3,000-$6,000 per battery depending on your qualifications — and it applies whether you're pairing a battery with brand-new solar or adding one to an existing system.

The urgency is real: as of mid-2026, roughly 25-40% of program funds remain, and once they're reserved, they're gone. This is a first-come program, not a permanent entitlement. Verify current status at sdcommunitypower.org — and if you've been on the fence about a battery, this rebate is the fence-remover.

If you live in Carlsbad, Del Mar, Escondido, Solana Beach, San Marcos, Oceanside, or Vista, Clean Energy Alliance's Solar Plus program is one of the most accessible offers in the country: solar + battery (or battery-only) with zero upfront cost and no credit check. Administered by CEA with Participate.Energy; Tesla designs, equips, and services the systems; payments land right on your utility bill; and all equipment replacements are covered for the minimum 25-year term.

The sleeper play I keep telling people about: battery-only for $0 down. If you already have solar, a battery lets you stop selling cheap at noon and buying expensive at 7pm — and maximize those nighttime sell-back credits. CEA also runs income-qualified programs (Battery Bonus Connect and Solar Plus Connect, funded through SGIP). Details: thecleanenergyalliance.org/solar-plus.

Net billing slashed export credits for most of the year — but during 1-2 hours a day in August and September, SDG&E pays $1 to $3.50 per kWh for power sent to the grid. That's up to 8x their own retail rate.

A well-designed solar + battery system charges itself on nearly-free sunshine all year, then cashes in during exactly those desperate late-summer peak hours. These credits are a major reason the best true-up date is July 1st (right before peak sun), and why proper system design in the net billing era can still get you to a ~$0 monthly bill. It takes software, your Green Button usage data, and a designer who actually cares. But the window is there.