A Southern California business writes two large checks it cannot avoid: one to the utility and one to the IRS. Commercial solar is one of the few investments that shrinks both — and the depreciation side is the half most owners have never had explained.
Most business owners know there is a federal tax credit for solar. Far fewer understand that the credit is only the first half of the tax story, and that the second half — depreciation — is often worth as much or more in the first year. Put together, the two can cut the effective cost of a qualifying commercial solar system by roughly half before the system has saved a single kilowatt-hour. That is what we mean when we say a tax liability can become an energy asset: money that was leaving the business as tax stays in the business as generating equipment on the roof or over the parking lot.
This post explains how that works for a Southern California business in 2026 — what changed in federal law last year, what California does and does not follow, and what the numbers look like on a real-sized system. It is not tax advice; it is the map you bring to your CPA.
Why this matters more in Southern California
Two facts frame everything that follows.
First, the electricity you are offsetting is the most expensive in the mainland United States. EIA data for spring 2026 put California’s average commercial rate at about 25.8¢ per kilowatt-hour against a national average of roughly 13.5¢. On SDG&E and Southern California Edison commercial time-of-use schedules, with demand charges layered on, the effective cost of a peak kilowatt-hour is higher still. Every dollar of solar production replaces a dollar bought at those prices.
Second, a profitable business in California carries a real tax bill — 21 percent federal on C-corporation income, up to 37 percent on pass-through income at the owner level, and the state’s own rates on top. Depreciation is a deduction against that income. The more you are paying, the more a large deduction is worth.
Together those two facts mean the same solar system is worth more to a San Diego or Orange County business than to one almost anywhere else: the savings are bigger because the rates are, and the deduction is bigger because the tax bill is.
Half one: the investment tax credit
Under Section 48E, a qualifying commercial solar project earns a federal investment tax credit of 30 percent of the eligible cost — a dollar-for-dollar reduction in the tax owed, not a deduction. Projects under 1 megawatt receive the full 30 percent without additional labor conditions; larger projects meet prevailing-wage and apprenticeship requirements to qualify for it. Bonus credits of ten points each are available for qualifying domestic content and for projects in designated energy communities.
One date matters more than any other in 2026. Under the law enacted in July 2025, a solar project that did not begin construction by July 4, 2026 must be placed in service by December 31, 2027 to claim the credit at all. Projects that did begin construction before that date have a longer runway. For a Southern California business considering solar today, that means the design, permitting and interconnection schedule has to land the system operating before the end of next year. Battery storage is not subject to the same deadline, which is one reason storage is being added to nearly every commercial project we design.
Half two: depreciation
A commercial solar system is business equipment, and business equipment is depreciated — its cost is deducted from taxable income over its recovery period. What changed in 2025 is how fast.
100 percent bonus depreciation is back, and it is permanent. The July 2025 law restored full first-year bonus depreciation for qualified property acquired and placed in service after January 19, 2025, with no phase-down schedule. A business can deduct the entire depreciable basis of a solar system in the year it goes into service.
The basis is 85 percent of the cost. When you claim the investment tax credit, the depreciable basis of the system is reduced by half the credit. With a 30 percent credit, that leaves 85 percent of the project cost as the amount you depreciate.
The old five-year schedule is gone — and it matters less than it sounds. For decades commercial solar sat in the five-year MACRS class. The same 2025 law removed that classification for projects whose construction began after December 31, 2024. Because bonus depreciation now lets a business deduct the full basis in year one, most owners will never miss the five-year table; the deduction simply arrives faster. Where it does matter is for owners who elect out of bonus depreciation or cannot use the full deduction in one year, and that is a conversation for the CPA.
What that looks like on a real system
Take a 200 kW commercial system in SDG&E or SCE territory at a representative $600,000 installed cost — the size and price range that fits a mid-size warehouse, a medical office group, a dealership or a retail center.
| Amount | |
|---|---|
| Installed cost | $600,000 |
| Investment tax credit (30%) | −$180,000 |
| Depreciable basis (cost less half the credit) | $510,000 |
| First-year bonus depreciation deduction | $510,000 |
| Federal tax saved on that deduction at 21% | −$107,100 |
| Effective first-year cost (C-corporation) | $312,900 |
That is a 48 percent reduction in effective cost in the first tax year for a C-corporation — before utility savings. For a pass-through business whose owner is in a higher bracket, the deduction is worth more: at a 37 percent marginal rate the same $510,000 deduction saves about $188,700, and the effective first-year cost falls to roughly $231,000, or around 60 percent off the installed price.
This is the “up to 50 percent” figure in our commercial spot. It is a potential reduction in effective cost for a qualifying business with the taxable income to absorb the deduction — not a guarantee, and not the same for every owner. But for a profitable Southern California business it is a realistic, defensible number, and it is available in the first year.
Then the utility savings start. On the rates above, a 200 kW system offsetting a Southern California commercial bill produces on the order of $70,000–$90,000 a year in avoided electricity and demand charges. Against an effective cost near $300,000, the system has paid for itself in three to four years and produces for another twenty-plus.
What California does — and does not — follow
The state side is where owners get surprised, and it belongs in the plan from the start.
California does not conform to federal bonus depreciation. The Franchise Tax Board does not allow the 100 percent first-year deduction; for state purposes the system is depreciated over its normal recovery period, and California’s own Section 179 expensing is capped at $25,000. The state deduction is real — it is just spread over years rather than taken at once. Your federal return and your California return will show different depreciation on the same asset, and your CPA will keep two schedules.
California has no state solar tax credit for businesses. The value on the state side comes from the utility bill, from local programs where they exist, and from property-tax treatment: under California’s active solar energy system exclusion, a system completed before the exclusion’s current sunset date of January 1, 2027 is not added to the building’s assessed value. Legislation to extend or narrow that sunset has been moving in Sacramento; as of this writing, a system finished in 2026 qualifies, and the Board of Equalization has published guidance on how partially complete projects are treated at the deadline. It is one more reason the 2026–2027 window matters.
Local and utility programs come and go. Storage incentives under the state’s SGIP program have been largely subscribed on the commercial side for several years; some community choice aggregators and municipal utilities in Southern California run their own programs. We check what is open at the time of design rather than assuming.
Who this works for
The depreciation half of the stack is worth the most to businesses that:
- are profitable, with federal taxable income large enough to use a six-figure deduction in one year (or carry the excess forward);
- own the building or have a long lease with the right to install and the horizon to benefit;
- run daytime-heavy loads — refrigeration, HVAC, manufacturing, medical equipment, EV charging — that solar can offset at retail value under the Net Billing Tariff;
- are on demand-metered rates where a battery can trim the peak, as we covered in How Commercial Solar and Battery Storage Cut Your Demand Charges.
Nonprofits, schools and government agencies do not pay income tax and cannot use depreciation, but they have their own path to the federal value through elective (“direct”) pay of the credit, or through a third-party ownership structure in which a taxable partner uses the credit and depreciation and passes the value through in the rate. That structure is common on faith-based and educational projects and is worth its own conversation.
The sequence that makes it work
The tax stack only pays if the project is timed and documented correctly:
- Confirm eligibility early — with your CPA, before the proposal is signed: entity type, taxable income, whether bonus depreciation or the five-year alternative fits, and how California’s non-conformity affects state estimates.
- Design to the placed-in-service deadline. A project starting now must be operating by December 31, 2027 to claim the credit. Permitting and utility interconnection, not construction, are the long poles in Southern California; the schedule should be built backward from that date.
- Document the basis. The eligible cost for the credit and the depreciable basis need clean, itemized records — including the carport structure if the array is over parking, and any storage that is charged from the array.
- Pair storage where the rates reward it. Storage keeps its credit eligibility longer, trims demand charges, and turns midday production into evening value under the Net Billing Tariff.
Stellar Solar has engineered and installed commercial solar and storage across Southern California since 1998 — A+ rated with the BBB and a repeat winner of San Diego’s Best Solar in the Union-Tribune Readers Poll. Call 866.787.6527 for a free commercial evaluation, or visit stellarsolarcommercial.com and we will build the tax-stack model on your building, your rate and your numbers.
Federal solar tax incentives and accelerated depreciation are subject to eligibility requirements and current tax law. This is not tax advice — consult your tax professional.
Sources & further reading
Incentives & tax
- IRS — Clean Electricity Investment Credit (Section 48E)
- IRS — Cost recovery for qualified clean energy facilities and property
- IRS — Form 4562 instructions (depreciation and amortization)
- SEIA — Depreciation of solar energy property (MACRS)
- DOE — Energy Communities (bonus credit eligibility)
Rates & utility savings
- U.S. EIA — electricity data and average commercial rates by state
- CPUC — Net Energy Metering / Net Billing Tariff
- SDG&E — business pricing plans
Stellar Solar credibility