Commercial Solar + Battery Storage ROI in 2026

The residential 25D tax credit ended after 2025, but the commercial picture is different — and stronger. Businesses look at the Clean Electricity Investment Credit (Section 48E ITC) on IRS Form 3468. A 30% base for projects that meet prevailing-wage and apprenticeship rules or fall under 1 MW, and two 10% adders sometimes described as reaching 50%, are commonly cited. They are not a settled quote. Commercial solar (§48E) is different — but the clock moved. Projects that missed the Jul 4, 2026 beginning-of-construction deadline generally must be placed in service by Dec 31, 2027. Figures on this page are general information, reviewed Oct 2026, not tax advice.

Unlike homeowners, businesses may also depreciate the system. Solar is often 5-year MACRS property, and bonus depreciation can change when that deduction is taken. Combined federal benefits are not a settled "more than half off" result for every project.

Lower installed cost per watt does the rest. Where a homeowner pays around $2.95/watt, commercial rooftop arrays install for roughly $1.20–$2.00/watt depending on scale — so the same incentives apply to a much cheaper starting price.

Under P.L. 119-21, solar projects that begin construction after July 4, 2026 generally must be placed in service by December 31, 2027 to keep Section 48E. IRS Notice 2025-42 generally requires the Physical Work Test — physical work of a significant nature, plus a continuous program of construction — to establish that construction began before July 5, 2026. The Five Percent Safe Harbor is limited to low-output solar facilities of not more than 1.5 MW AC, subject to aggregation rules. Reviewed Oct 2026. General information, not tax advice.

The deadline is a reason to scope timing early, not the whole case for solar: the underlying economics — the credit, depreciation, and energy savings — remain compelling for projects that plan ahead.

Installed-cost ranges reflect commercial-scale benchmarks published by the National Renewable Energy Laboratory (NREL), which consistently show C&I systems pricing well below residential on a per-watt basis. Production estimates use state-level sun-hour data in the same PVWatts tradition NREL maintains.

The incentive treatment follows the Internal Revenue Service's framework for the Section 48E Clean Electricity Investment Credit and 5-year MACRS depreciation under the modified accelerated cost-recovery system. According to the U.S. Department of Energy, pairing the investment credit with accelerated depreciation is the core of commercial solar economics — and the reason business payback periods run shorter than residential ones.

We model the depreciation shield at a combined federal-plus-state rate near 26% and reduce the depreciable basis by half the credit claimed, consistent with current IRS guidance. These are planning estimates, not a substitute for advice from a qualified tax professional.