Understanding your commercial ITC rate
The base rate: 30% or 6%
The base rate is 30% if your project meets prevailing wage and apprenticeship requirements, or if it's under 1 MW, which qualifies automatically. Without meeting those requirements, the base rate is just 6%. Stacking bonus adders on top of the 30% base can push the total rate as high as 70%, though most projects land in the 30% to 50% range. Almost every commercial rooftop system on this site's radar, meaning anything from a small storefront to a large warehouse, comfortably clears the under-1-MW threshold. For the official rules on depreciation methods and recovery periods that pair with this credit, IRS Publication 946 covers how MACRS applies to business property, including solar equipment. A size estimate is only half the decision for a business. The cash purchase vs financed payback comparison in our Financing section can help you work out which way to pay for the system costs less.
The three bonus adders, stacked one at a time
Three adders can stack on the base rate under Section 48E: a domestic content adder worth 10% for projects meeting US manufacturing thresholds, an energy community adder worth 10% for sites in areas affected by fossil fuel job or plant closures, and a low-income community adder worth 10% to 20% for qualifying projects, which is application-based and capacity-limited each year. Ask your installer to check your address against the DOE's energy community and low-income community maps before you assume you don't qualify, and the IRS's own Low-Income Communities Bonus Credit Program page lists the current program year's application window and capacity limits by category. The bonus depreciation calculator shows how these savings compound with your depreciation timeline.
The 2026 deadline picture, updated
The July 4, 2026 safe harbor deadline for the extended construction window has passed, so most new projects starting now must be placed in service by December 31, 2027 to claim the credit. Projects that safe-harbored construction before that date have until roughly 2029 to 2030 to finish and still qualify at the locked-in rate. If your project is still in the planning stage, treat December 31, 2027 as the real deadline and build your timeline backward from there with your installer, and weigh it against options in the loan vs. cash comparison if financing timing matters to your decision, or the rebate plus ITC combined calculator in our rebates and incentives section to see how a state or utility rebate stacks with the federal rate before that deadline.
Turning your ITC rate into cash flow
Once you know your total rate, the credit reduces your tax bill dollar for dollar, and it also reduces your MACRS depreciable basis by half its value. Run your ITC amount through the payback calculator to see how it combines with depreciation for your full year-one cost recovery, and the financing cost with ITC applied tool to see how that credit changes the numbers if you're financing rather than paying cash.