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Solar + Battery vs. Solar Only in Illinois

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 Illinois 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 $7,460. Whether a battery adds to this depends entirely on your utility's rate structure. Illinois has 1 major utility with TOU rates, creating real arbitrage opportunities.

Battery Economics: Commonwealth Edison (ComEd)

$8,400
Battery Net Cost
$1
Daily Arbitrage
$399
Annual Value
-$5,486
25-Year Battery NPV

For Commonwealth Edison (ComEd) customers, battery storage has marginal economics with a 25-year NPV of -$5,486. The limited peak/off-peak spread means TOU arbitrage alone doesn't justify the cost. Backup power value and future grid services programs could improve the case.

Combined System Value

ConfigurationNet Cost25-Year NPV
Solar only (7 kW)$14,210$7,460
Battery only (13.5 kWh)$8,400-$5,486
Solar + Battery$22,610$1,974

Frequently Asked Questions

Is solar + battery worth it in Illinois?
With Illinois's average utility rate of $16.2¢/kWh and solar irradiance of 1,200 kWh/kW/yr, the 25-year NPV for a 7 kW solar system is $7,460. Battery value depends on your utility's TOU rate structure.
What incentives are available for solar + battery in Illinois?
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 Illinois?
Solar panels in Illinois pay back in approximately 10 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 Illinois

Solar vs Grid›Heat Pump›Full Electrification›

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