Commercial Solar Depreciation: MACRS and Bonus Rules for 2026

For many business owners, the decision to go solar hinges on more than just lower electric bills. The financial case often depends on how quickly you can recover your investment through depreciation and tax credits. In 2026, the rules for commercial solar depreciation, specifically MACRS and bonus depreciation, create a powerful opportunity to accelerate deductions and improve cash flow. But the details matter: the interaction between the investment tax credit (ITC) and bonus depreciation, the phase-down of bonus rates, and the choice of depreciation schedules can significantly alter your year-one tax savings. This guide breaks down the essentials so you can ask the right questions and model your project accurately.

MACRS Five-Year Schedule Basics for Solar Property

Most commercial solar arrays qualify as five-year property under the Modified Accelerated Cost Recovery System (MACRS). This means the IRS allows you to depreciate the system over a five-year recovery period using an accelerated method, typically the 200 percent declining balance method with a switch to straight-line. The practical effect is that you deduct a larger portion of the system's cost in the early years, which can be especially valuable if you want to offset taxable income quickly.

The MACRS schedule for five-year property is predetermined: 20 percent in year one, 32 percent in year two, 19.2 percent in year three, 11.52 percent in year four, 11.52 percent in year five, and 5.76 percent in year six. This half-year convention assumes the property is placed in service midway through the first year, regardless of the actual installation date. For solar projects, that convention usually applies unless you elect to use the mid-quarter convention, which is rarely beneficial for solar unless a large portion of your assets are placed in service in the last quarter.

The depreciable basis for MACRS is not the full system cost if you claim the commercial ITC. You must reduce the basis by 50 percent of the ITC amount. For example, if your system costs $1 million and you earn a 30 percent ITC ($300,000), your depreciable basis becomes $850,000 (i.e., $1,000,000 minus $150,000). This basis reduction is a critical step that many owners overlook when modeling year-one deductions. The remaining basis is then depreciated according to the MACRS schedule, and if bonus depreciation is claimed, it further accelerates the recovery.

How Bonus Depreciation Changes Year-One Deductions

Bonus depreciation is an additional first-year deduction that allows you to recover a specified percentage of the cost of qualifying property on top of the regular MACRS depreciation. For solar property, bonus depreciation can be applied to the depreciable basis after the ITC basis reduction. The bonus rate has been phasing down since 2023: it was 80 percent in 2023, 60 percent in 2024, 40 percent in 2025, and is scheduled to be 20 percent in 2026. This means that for projects placed in service in 2026, you can deduct 20 percent of the depreciable basis immediately, with the remaining 80 percent depreciated under the standard MACRS schedule.

To illustrate, consider a $1 million commercial solar system with a 30 percent ITC. The depreciable basis is $850,000. With a 20 percent bonus depreciation in 2026, you can deduct $170,000 in year one as bonus depreciation. The remaining $680,000 is depreciated under MACRS: 20 percent of that ($136,000) is deductible in year one as regular depreciation (subject to the half-year convention). So total year-one depreciation is $170,000 + $136,000 = $306,000. That is a substantial deduction that can offset a large portion of your taxable income from the project or other business activities.

It is important to note that bonus depreciation is optional. You can elect to use a lower rate or forgo it entirely, which might make sense if you expect higher taxable income in future years or if you want to spread deductions more evenly. However, for most businesses, claiming the available bonus depreciation in 2026 is advantageous because it accelerates cash flow and reduces the time to break even. Keep in mind that bonus depreciation applies to the taxpayer's depreciable basis after the ITC reduction, and the combined deductions cannot exceed the system's cost.

Interaction with the Commercial ITC Base and Adders

The commercial investment tax credit (ITC) is a dollar-for-dollar credit against federal income tax, generally equal to 30 percent of the system cost for projects that meet prevailing wage and apprenticeship requirements (or 6 percent if those requirements are not met). The ITC base can be increased by adders for domestic content (10 percent), energy community (10 percent), and low-income community (10 to 20 percent), potentially raising the total credit to as high as 50 percent or more. However, the ITC and depreciation interact in two key ways: the basis reduction rule and the potential for adders to affect the depreciable basis.

As mentioned, the depreciable basis for MACRS is reduced by 50 percent of the ITC claimed. This means that if you claim a 30 percent ITC, your basis is reduced by 15 percent of the system cost. If you qualify for adders, the ITC amount increases, and the basis reduction also increases. For example, a 40 percent ITC would reduce the basis by 20 percent. This interplay means that while adders boost your tax credit, they also reduce the amount you can depreciate. The net benefit of adders is still positive, but it is important to model the combined effect accurately.

Additionally, some adders, such as the low-income community bonus, may have specific rules that affect depreciation. For instance, the low-income community bonus credit is allocated through a competitive program and may come with separate basis adjustment rules. Always consult a tax advisor to understand how each adder affects your depreciable basis. In general, maximizing the ITC is usually the priority because it is a direct credit, but the timing of depreciation deductions can influence your overall after-tax return.

Questions to Bring to a Tax Advisor Before Signing

Before you commit to a commercial solar project, it is wise to consult with a tax advisor who specializes in renewable energy incentives. The rules are complex and can change, and your specific tax situation will determine the optimal strategy. To make the most of your meeting, prepare a list of questions that cover the key areas of depreciation, ITC, and project timing. Below are some essential questions to ask, followed by a brief explanation of why each matters.

• What is my depreciable basis after the ITC and any adders? This determines the amount you can depreciate and is the starting point for all calculations.
• Should I claim bonus depreciation in 2026 or elect out? The decision depends on your expected taxable income in future years and your cash flow needs.
• How does the half-year convention affect my year-one deduction? The timing of placing the system in service can impact the depreciation schedule, especially if you are near year-end.
• Do I qualify for any ITC adders, and how do they affect my basis? Adders can increase your credit but also reduce your depreciable basis, so you need to model the net effect.
• Are there state-level depreciation or incentive rules that differ from federal rules? Many states offer additional incentives or have different depreciation rules that can impact your overall savings.

These questions will help your advisor provide tailored guidance and avoid costly mistakes. For a deeper look at how depreciation and incentives play out in real projects, see our 2026 commercial solar savings case studies, which illustrate how businesses have leveraged these rules to maximize returns.

In addition to these questions, consider the financing structure. If you use a power purchase agreement (PPA) or lease, the tax benefits may accrue to the financier rather than to you. If you own the system, you capture the depreciation and ITC directly. Your advisor can help you compare ownership versus third-party financing. Also, be sure to discuss the timing of the project: placing the system in service by December 31, 2026, is necessary to claim the 2026 bonus rate and ITC for that year. If the project slips into 2027, the bonus rate may be lower (or zero, depending on legislative changes), so schedule accordingly.

Finally, remember that tax laws can change. The bonus depreciation phase-down is currently scheduled, but Congress could modify it. The ITC for solar is also subject to long-term extensions and changes. Working with a tax advisor who stays current on renewable energy policy will help you navigate these uncertainties. For additional resources on solar incentives and to connect with vetted solar professionals, you can explore free solar power quotes to compare options and ensure you are getting competitive pricing, which ultimately enhances the value of your tax benefits.

Commercial solar depreciation in 2026 offers a valuable opportunity to accelerate tax deductions and improve project economics. By understanding the MACRS five-year schedule, the 20 percent bonus depreciation rate, and the interaction with the ITC, you can make informed decisions that align with your business goals. Bringing the right questions to your tax advisor will help you avoid surprises and maximize your return on investment.