How Does Cost Segregation Work for Electrical Contractors?

Which electrical work is 5-year, and which stays structural

Not all electrical work depreciates the same way. Core building wiring, the main electrical service, and general-purpose circuits are part of the structural shell, on the standard 39-year (commercial) or 27.5-year (residential rental) schedule. Electrical work serving specific equipment or fixtures, dedicated circuits for kitchen equipment, medical equipment, or process machinery, and certain decorative and specialty lighting, sits in the 5-year class instead, a category a cost segregation study is built specifically to pull out of the general building basis.

An electrician running a bid does not need to sort components into depreciation classes on the spot. What matters for the sales conversation is knowing that this distinction exists, so a proposal can flag which parts of a job are the kind of work a study would pull into a faster schedule, without the electrician assigning a class or a dollar figure themselves.

A commercial tenant fit-out is where this split shows up most clearly: the new electrical panel and service upgrade serving the whole space sit closer to structural, while the outlets and circuits wired specifically for a kitchen line, a server room, or specialty equipment sit on the faster side. A single fit-out invoice can carry both categories at once.

LED retrofits and specialty lighting

An LED lighting retrofit is one of the clearest everyday examples. Decorative and specialty lighting fixtures generally sit in the 5-year class, separate from the structural electrical service feeding them. A retrofit that swaps out fixtures across a retail space, an office, or a restaurant is touching 5-year property directly, work that a cost segregation study identifies and accelerates using current bonus depreciation rules under section 168(k), which restores 100% bonus for qualified property acquired after January 19, 2025.

Retail spaces, restaurants, and offices all run this kind of retrofit regularly, whether for energy savings or a straightforward refresh. Whatever the motivation for the job, the depreciation treatment of the fixtures themselves does not change; the retrofit is retrofit, and the classification question is the same one a study answers on any other job.

Owners sometimes fund a retrofit through a utility rebate or incentive program, which is a separate arrangement from how the fixtures depreciate on the tax return. Whether an owner used a rebate to reduce the up-front cost does not change how the study classifies the fixtures that were installed.

Fire protection and alarm systems: the 179 QRP angle

Fire protection and alarm systems get their own separate mechanic: section 179 qualified real property lets an owner of NONRESIDENTIAL property expense these systems, along with roofs, HVAC, and security systems, in the year placed in service, instead of depreciating them over 39 years. That applies to a new fire alarm panel, sprinkler system work, or security system installation on a commercial building, placed in service after the building itself, subject to annual dollar and business income limits. It does not apply to residential rental property.

A single electrical contract sometimes covers both categories at once, a fire alarm panel replacement bundled with new decorative lighting in the same renovation. Each component follows its own rule: the alarm system checked against the 179 QRP test, the lighting checked against the 5-year class, both handled by the same underlying study rather than by the contractor guessing which bucket applies.

Replacing a panel or system: the partial asset disposition angle

Replacing an electrical panel, a fire alarm system, or a lighting system triggers partial asset disposition under Treas. Reg. 1.168(i)-8 on the OLD component: its remaining depreciable basis can be written off, but only in the tax year of the replacement. Miss that year and the old system's basis stays buried in the building's depreciation schedule for decades, while the new system starts its own schedule on top of it.

The table holds for a single-tenant building as well as a multi-tenant one; each tenant space's dedicated circuits and fixtures are treated separately from the building's core electrical service, which stays with the landlord's structural basis regardless of how many tenants the space serves.

What an electrical rep can say

• Say: "Replacing this panel and lighting this year is what opens the door to writing off the old system's remaining value, in this same tax year."
• Don't say: "You'll cut your tax bill by doing this now."
• Say: "Since this fire alarm work is on a nonresidential building, it may qualify for section 179 expensing, subject to the usual limits. A cost segregation study is what confirms the number."
• Don't say: "You qualify," as a flat statement about the customer's own return.

The same restraint holds for a straightforward LED retrofit quote. An electrician can note that the fixtures being installed are the kind of property a study accelerates, without ever naming a dollar figure the customer should expect back.

Where the number comes from

The number comes from a free estimate, the 60-second qualifier at /qualify, which models the building's likely first-year acceleration, including any electrical or lighting components and disposition events, before the owner commits to a study. See our contractor hub for how these same mechanics work across other trades.

An electrical contractor who routes every eligible job, panel swaps, alarm installs, lighting retrofits, to the same estimate link builds a consistent habit that costs nothing extra to repeat and gives every customer the same chance to check the number with their own CPA.

Frequently asked questions

Is all the electrical work in a commercial building 5-year property?

No. Core building wiring and general electrical service stay on the standard 39-year commercial schedule. Electrical work serving specific equipment, like dedicated kitchen or medical circuits, or specialty and decorative lighting, can sit in the 5-year class instead.

Does an LED lighting retrofit qualify for accelerated depreciation?

Decorative and specialty lighting fixtures generally sit in the 5-year class, which is bonus-eligible under current rules. A cost segregation study is what identifies and separates this lighting from the building's core structural electrical service.

Can a fire alarm system be expensed under section 179?

Fire protection and alarm systems can qualify for section 179 qualified real property expensing on nonresidential buildings, placed in service after the building itself, subject to annual dollar and business income limits. The provision does not apply to residential rental property.

What happens to the old panel's value when it gets replaced?

Replacing an electrical panel triggers partial asset disposition on the old one: its remaining depreciable basis can be written off, but only in the tax year of the replacement. Miss that year and the old panel's basis stays on the building's original schedule.

Can an electrical contractor tell a customer exactly how much they will save?

No. A rep should describe the mechanic and its timing, not assert a specific savings figure for the customer's own return. The dollar number comes from a cost segregation study and the owner's CPA, not from the sales conversation.