Solar + Battery Economics

What batteries cost in 2026

Installed, a residential battery runs roughly $1,000–$2,000/kWh. A 13.5 kWh system (Powerwall 3-class) lands around $13,000–$17,000 installed depending on market and complexity. The federal residential battery credit is $0 in 2026 (§25D expired). State programs (CA, NY, MA, CO and others) can reduce this — verify before budgeting.

The honest arbitrage math

A battery earns money by shifting energy: charge from solar (or cheap grid) when power is cheap, discharge when it’s expensive. In round numbers, a 13.5 kWh battery can shift maybe 10 kWh/day of meaningful arbitrage. At a rate spread of 25¢/kWh (a big spread), that’s $2.50/day ≈ $900/year. Against a $15,000 installed cost, that’s a ~17-year payback — longer than most battery warranties. Under net billing (CA NEM 3.0), the spread is export price vs evening retail, which is larger; under 1:1 retail net metering, a battery earns almost nothing on arbitrage because exports are already worth the retail rate.

Conclusion: on pure energy math, most batteries do not pay for themselves. Anyone who tells you otherwise is usually assuming a rate structure that favors the pitch. Model your own numbers in the battery calculator.

Where batteries do make sense

• Outage resilience: the primary real-world reason. If your area has frequent or long outages (hurricanes, wildfire shutoffs, winter storms, ERCOT events), a battery’s value is avoided outage costs and comfort — a genuine purchase, just not one with a payback number.
• Net-billing / low-export markets: where exports pay ~5–10¢/kWh, storing for evening use at 30–50¢ can be worthwhile. This is the CA NEM 3.0 story.
• TOU + demand charges: some utilities charge demand fees or steep on-peak rates; a battery can shave both. Tariff-specific — check yours.
• Future-proofing: rate designs are moving toward lower export compensation; a battery hedges that change.

Backup: size the battery to the load, not the roof

Whole-home backup is expensive (big inverter + big battery). Most homes run fine on essential loads: fridge, lights, internet, a few outlets. A 13.5 kWh battery at a 1,200 W load runs about 11 hours — enough to ride out most outages, especially if you ration. Check the battery’s continuous power rating (e.g., 5–11.5 kW) against your loads, and remember: “usable kWh” is the number that matters, not the raw capacity. Try the backup estimator.

Solar-only vs solar + battery payback

Adding a battery raises your net cost by its full installed price (no federal credit in 2026) while adding only incremental savings — extra self-consumption minus lost export value. Our calculator shows three numbers: solar-only payback, solar+battery payback, and the honest incremental battery payback. If the incremental payback is 15+ years, treat the battery as resilience, not investment — and be at peace with that decision.

Questions to ask an installer

• What usable kWh, continuous power, and round-trip efficiency does the battery have?
• What exactly is included in the battery price (gateway, sub-panel, permit)?
• Does it qualify for any current state/utility incentive, and is that in the price?
• Can it power my essentials (or whole home) in an outage, and how is that wired?
• What is the warranty — years, cycles, and capacity guarantee?

Buy the battery if the resilience is worth the price to you. Don’t buy it because someone promised it “pays for itself” — the math usually says otherwise, and we show it to you.