The depreciation life of a generator under IRS rules is usually either 7 years or 20 years, depending on how the generator is used and where it’s installed. A permanently installed industrial generator that feeds a building’s electrical system is 20-year property. A portable or smaller generator that doesn’t fit an industrial classification defaults to 7-year property. Generators serving residential rental activity are typically 5-year property. In 2026, the assigned recovery period matters less than it used to, because 100 percent bonus depreciation and Section 179 expensing let most businesses deduct the full cost in the first year.
Recovery Period by Type of Generator
The Modified Accelerated Cost Recovery System (MACRS) is the required depreciation framework for nearly all tangible business property placed in service after 1986. You don’t pick a useful life; the IRS assigns each asset to a class, and the class controls the recovery period.1Internal Revenue Service. Publication 946 (2024), How To Depreciate Property For generators, three classifications cover most situations.
Industrial and Building-Integrated Generators: 20 Years
The asset class aimed directly at generators is 00.4, “Industrial Steam and Electric Generation and/or Distribution Systems.” It covers equipment used to generate or distribute electricity and steam as part of a facility’s infrastructure. A permanently installed standby or prime-power generator that feeds into a building’s electrical system falls here. Asset Class 00.4 has a class life of 28 years, a 20-year recovery period under the General Depreciation System (GDS), and a 28-year period under the Alternative Depreciation System (ADS).2Internal Revenue Service. Publication 946 (2024), How To Depreciate Property – Appendix B Table of Class Lives and Recovery Periods
Utility-scale generators sit in a different class with the same 20-year period. Asset Class 49.13 covers electric utility steam production plants, including combustion turbines, electric generators, and related distribution systems used to produce electricity for sale.2Internal Revenue Service. Publication 946 (2024), How To Depreciate Property – Appendix B Table of Class Lives and Recovery Periods Generators in other industries can fall into that industry’s own asset class instead; a generator powering equipment at a petroleum refinery, for instance, would be classified under the refinery’s class rather than 00.4.
Portable and Small Generators: 7 Years
Not every generator qualifies as an “industrial steam and electric generation system.” A portable unit you move between job sites, or a small generator that plugs into specific equipment, may not fit that description. When property has no designated class life and no statute assigns it to a particular class, it defaults to 7-year property under GDS.3Internal Revenue Service. 2025 Instructions for Form 4562 – Depreciation and Amortization Many small business generators end up here, and the shorter period matters if you can’t or don’t want to expense the cost in year one.
Generators at Residential Rental Properties: 5 Years
Install a generator at a residential rental property and the classification shifts again. Publication 527 lists appliances, carpeting, and furniture used in residential rental activities as 5-year property. Generators aren’t named, but the IRS treats similar equipment such as dishwashers as 5-year property in its examples.4Internal Revenue Service. Publication 527 (2025), Residential Rental Property A standalone generator serving a rental building is most likely 5-year personal property used in the rental activity. The building and its structural components remain on the 27.5-year residential schedule.
When You Must Use ADS Instead
GDS is the default, and it’s what most businesses want because it recovers cost faster with accelerated methods. ADS is mandatory in specific situations, including property used predominantly outside the United States and property used in a tax-exempt activity. ADS generally uses the full class life with straight-line depreciation, so a 00.4-class generator on ADS stretches to 28 years. You can also elect ADS voluntarily, though it’s rarely the better choice.
Deducting the Full Cost in Year One
For generators bought and placed in service in 2026, the recovery period is often a background number rather than a driver of the actual deduction. Two accelerated expensing options can absorb the whole cost.
100 Percent Bonus Depreciation
The One, Big, Beautiful Bill (OBBB), signed in 2025, restored permanent 100 percent bonus depreciation for qualified property acquired after January 19, 2025.5Internal Revenue Service. Treasury, IRS Issue Guidance on the Additional First Year Depreciation Deduction Amended as Part of the One, Big, Beautiful Bill Property qualifies if it has a MACRS recovery period of 20 years or less, which covers every generator classification above. New and used generators both qualify, provided the used equipment wasn’t previously used by the same taxpayer. For used property, the acquisition date is set by when you entered a binding contract or took physical possession, depending on the circumstances.6Internal Revenue Service. IRS Notice 2026-11 – Interim Guidance on Additional First Year Depreciation Deduction
Bonus depreciation has no annual dollar cap, and unlike Section 179, it can create or increase a net operating loss. If you choose not to claim bonus depreciation on a particular class of property, you must make that election on your return, and it applies to every asset in that class placed in service during the year.
Timing matters here. If you acquired a generator before January 20, 2025, the older phase-down schedule still applies: 40 percent bonus for property placed in service during 2025 and 20 percent for 2026. Property acquired after January 19, 2025, and placed in service the same year jumps straight to 100 percent under the OBBB.
Section 179 Expensing
Section 179 is the other route to a first-year write-off. You elect to expense the cost of qualifying property in the year you place it in service. Generators qualify because they’re tangible personal property used in the active conduct of a business.7Office of the Law Revision Counsel. 26 USC 179 – Election to Expense Certain Depreciable Business Assets
For tax years beginning in 2026, the maximum Section 179 deduction is $2,560,000, phasing out dollar-for-dollar once total Section 179 property placed in service during the year exceeds $4,090,000.8Internal Revenue Service. Revenue Procedure 2025-32 Both figures are indexed for inflation.
The catch is that Section 179 can’t exceed your taxable income from the active conduct of any trade or business. Buy an $80,000 generator with $50,000 of business income, and you deduct $50,000 this year and carry $30,000 forward. Bonus depreciation has no such income cap, which is why many businesses take bonus first and use Section 179 to target specific assets when it helps.
How the Deduction Works If You Don’t Expense It Up Front
If you don’t take full first-year expensing, the remaining basis is spread over the recovery period using a convention and a calculation method.
The half-year convention is the default. It treats property as placed in service at the midpoint of the tax year, giving you half a year’s depreciation in year one and half in the final year. The mid-quarter convention overrides that default if more than 40 percent of the total depreciable basis of property you placed in service that year went in during the last three months.9Office of the Law Revision Counsel. 26 USC 168 – Accelerated Cost Recovery System Buying a generator in December with little other property placed in service earlier that year is the classic trigger. When it applies, each asset is depreciated based on the quarter it entered service.
GDS property with a recovery period of 20 years or less uses the 200 percent declining balance method, which front-loads deductions at double the straight-line rate. Seven-year property starts at roughly 28.6 percent of the declining balance; 20-year property starts at 10 percent. The method automatically switches to straight-line the year straight-line produces a larger deduction, ensuring full recovery by the end of the period. You don’t need to run the switchover math yourself. Publication 946 has percentage tables for every property class and convention that give you the exact deduction for each year.
Repairs and Improvements After the Generator Is in Service
Money you spend on the generator after it’s running creates a separate question: deductible repair, or capital improvement that starts its own depreciation schedule? The IRS tangible property regulations use three tests. An expenditure is a capital improvement if it results in a betterment, a restoration, or an adaptation to a new or different use.10Internal Revenue Service. Tangible Property Final Regulations
Replacing a worn belt or changing the oil is a routine repair, fully deductible that year. Replacing the engine block, or converting the unit from diesel to natural gas, crosses into improvement territory because those expenses either restore a major component or adapt the equipment to a different use. Improvements must be capitalized and depreciated fresh from the date the improvement is placed in service.
Smaller expenditures may qualify for the de minimis safe harbor, which lets you deduct amounts up to $5,000 per item if you have an applicable financial statement (audited financials or similar), or $2,500 per item if you don’t.10Internal Revenue Service. Tangible Property Final Regulations Generator parts and minor components often fall below these thresholds.
Selling the Generator: Depreciation Recapture
Sell a generator for more than its adjusted basis (original cost minus accumulated depreciation) and the IRS recaptures the depreciation you claimed. Under Section 1245, the gain is taxed as ordinary income up to the total depreciation deducted. Only gain above the original purchase price gets capital gains treatment.11Office of the Law Revision Counsel. 26 U.S. Code 1245 – Gain From Dispositions of Certain Depreciable Property
Say you bought a generator for $50,000, wrote off the full $50,000 (adjusted basis zero), and later sold it for $15,000. The entire $15,000 gain is ordinary income. Recapture works the same whether you deducted the cost through regular MACRS, bonus depreciation, or Section 179. The faster you wrote it off, the more recapture is possible on sale. Time value of money still generally favors taking the deduction sooner; the sale simply shouldn’t surprise you.
A Note on State Tax Conformity
Federal depreciation doesn’t automatically flow to your state return. More than 20 states decouple from federal bonus depreciation, requiring an addback and a slower state-level schedule. Some states allow a matching subtraction spread over several years; others disallow the acceleration entirely. State rules change often as legislatures respond to federal changes like the OBBB, so check with your state tax authority or a tax professional before assuming the federal treatment carries over.