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Solar + Battery vs. Solar Only in California

Does adding battery storage improve your solar ROI? Analysis of TOU arbitrage value, net metering export losses, and backup power economics.

Adding a 13.5 kWh battery to a solar system in California changes the economics in three ways: it enables time-of-use (TOU) arbitrage, reduces export losses under unfavorable net metering policies, and provides backup power during outages.

The solar system alone produces a 25-year NPV of $41,579. Whether a battery adds to this depends entirely on your utility's rate structure. California has 3 major utilities with TOU rates, creating real arbitrage opportunities.

Battery Economics: San Diego Gas & Electric (SDG&E)

$8,400
Battery Net Cost
$4
Daily Arbitrage
$1,463
Annual Value
$10,238
25-Year Battery NPV

For San Diego Gas & Electric (SDG&E) customers, adding a 13.5 kWh battery increases total system NPV by $10,238. The battery generates $1,463/year in TOU arbitrage by storing solar during off-peak ($14.0¢/kWh) and discharging during peak ($58.0¢/kWh).

Combined System Value

ConfigurationNet Cost25-Year NPV
Solar only (7 kW)$13,573$41,579
Battery only (13.5 kWh)$8,400$10,238
Solar + Battery$21,973$51,817

Frequently Asked Questions

Is solar + battery worth it in California?
With California's average utility rate of $28.2¢/kWh and solar irradiance of 1,600 kWh/kW/yr, the 25-year NPV for a 7 kW solar system is $41,579. Battery value depends on your utility's TOU rate structure.
What incentives are available for solar + battery in California?
The federal IRA provides a 30% ITC for solar and battery installations (through 2032) and up to $2,000 in 25C credits for heat pumps. Income-qualified households may receive additional point-of-sale rebates through the HOMES and HEAR programs.
How long does solar + battery take to pay back in California?
Solar panels in California pay back in approximately 5 years. Battery payback depends on TOU rate spreads. Heat pump payback ranges from 5-12 years depending on current fuel costs and local electricity rates.

Other Comparisons for California

Solar vs Grid›Heat Pump›Full Electrification›

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