Home battery installation: process, permits, and timeline

Most of a home battery installation is not the installation. The physical work is typically a day or two of electrical labor. What surrounds it is a site assessment, a sizing decision you should make rather than accept, a local permit, a fire code review, a utility interconnection application, an inspection, and finally a commissioning session where the system is configured to do what you actually bought it for.

This page walks that sequence in order, so you can tell a normal delay from a badly run job. An installed system commonly runs roughly $10,000 to $20,000 before incentives, which is enough money to be worth understanding what each step is for.

Site assessment

The first visit is about constraints, not products. A competent assessor is checking your electrical service size and main breaker rating, the condition and available space in your panel, where the meter sits, and whether the service can support the equipment without an upgrade. A panel upgrade is the single most common cost surprise in this category, and it is better discovered now than after a contract.

They are also finding a legal location for the battery. Siting is governed by fire code, not preference: permitted locations, clearances from doors and windows, wall protection requirements, and whether an impact barrier is needed in a garage all come from the version of NFPA 855 your jurisdiction has adopted. Temperature matters too, since a garage that swings to extremes affects both performance and, on some products, warranty conditions.

The last thing the assessment should settle is scope. Do you want the whole house backed up, or a subset of essential circuits? That answer drives the size, the cost, and the panel work, and it is worth deciding before you look at hardware. Our whole-home versus essential backup explainer covers the trade.

Sizing

Two numbers matter and they are not the same. Capacity in kilowatt-hours determines how long you can run. Power in kilowatts determines what you can run at once. A battery with plenty of stored energy and modest continuous output will not start a large air conditioner; a battery with high surge capability and little capacity will start it and then run out. Our kWh versus kW explainer covers the distinction, and the specifications for every model we track list both, quoted on each manufacturer's own basis.

Do this part yourself before an installer does it for you. Run your actual usage, your rate plan, and your outage history through the calculator. An installer's sizing proposal is a reasonable input; it should not be the only one, since the incentive to oversize is obvious.

Permits and code review

Your installer files with the authority having jurisdiction, usually a city or county building department. Expect a building and electrical permit, and expect the fire code side to be reviewed as part of it. The relevant documents are NFPA 855, the Standard for the Installation of Stationary Energy Storage Systems, and NEC Article 706, which covers energy storage systems. The equipment itself is normally expected to carry a UL 9540 listing, with UL 9540A large-scale fire testing used when installation conditions fall outside the default code limits.

We are not going to publish a permit fee figure, because fees are set locally and vary enormously. Ask your installer for the line item, itemized, and ask whether it is included in the quoted price or billed through.

Timing is the question everyone asks, and the honest answer is that it depends on your jurisdiction. There is real published data on one specific mechanism. SolarAPP+, an automated permitting platform developed by the National Renewable Energy Laboratory, issues instant permits for code-compliant residential solar applications. NREL's performance review of its first full year found that permit review duration dropped from about 9 days for traditionally permitted projects to zero for SolarAPP+ projects, and that a typical project was permitted, installed, and inspected roughly 13 days sooner overall, about 32 days versus about 45 days through the traditional process. NREL also reported that SolarAPP+ projects were roughly 37 percent less likely to fail inspection.

Three caveats before you take those numbers as a schedule. They come from NREL's review of 2021 data in the jurisdictions that had adopted the platform, most jurisdictions have not, and NREL reports durations in business days, so read 32 versus 45 as business days, not calendar days. They describe solar PV projects, and the one published storage result points the other way: NREL's follow-up review of 2022 data reported that across the seven jurisdictions with enough storage projects to compare, median permit-to-inspection durations for solar-plus-storage were longer for SolarAPP+ projects than for traditionally permitted ones, 64 versus 55 days. The solar speedup has not been demonstrated for battery projects. And they measure the permitting portion, not the whole project from contract to switch-on. Use them as evidence that permitting speed varies by process, not as a promise about your house.

Interconnection

This is a separate track from your building permit, run by your utility rather than your city, and it is the step people most often do not know exists.

Any battery that can interact with the grid, meaning it charges from the grid, exports, or is paired with solar, requires an interconnection application and, at the end, permission to operate. The utility reviews the equipment, the system size, and how it will behave, then issues written authorization to energize. The application generally goes in early, because it runs on the utility's own queue in parallel with the local permit.

In California, this is where the net billing tariff attaches, since your interconnection application date determines which export rules and which required rate plan apply to you. If you are pairing with solar there, read our NEM 3.0 guide before the application goes in, not after.

Ask your installer, in writing, who files the interconnection application, when it will be filed, and what the utility's current stated processing window is. A quote that treats permitting and interconnection as one line item is hiding the step that most often sets the calendar.

Installation day

The physical work is usually one to two days for a straightforward job, longer if a panel upgrade or a backup loads subpanel is involved.

What happens: the battery is mounted or set on its pad and secured, conduit is run, and the system is tied into your electrical service through a listed disconnect. If you chose essential-circuit backup, the circuits you want protected are moved to a dedicated backup subpanel. If you chose whole-home backup, the tie-in happens at the service level, through whatever gateway, transfer switch, or meter collar the product uses. Communication hardware is set up so the system can be monitored.

At the end of this the system is installed but not authorized. Do not expect it to be doing anything useful yet.

Inspection

A local inspector visits and checks the work against the adopted code: siting and clearances, conductor sizing and protection, labeling, disconnect location and accessibility, and equipment listing. Corrections are common and not a scandal; a failed first inspection with a same-week correction is a normal outcome, not evidence of a bad installer.

Once the local inspection passes, the result typically goes to the utility, and permission to operate follows on the utility's timeline. Until that arrives, an installer should not be energizing a grid-interactive system.

Commissioning

The last step is the one most likely to be rushed, and it is the one that determines whether the battery earns anything.

Commissioning is where operating modes are configured: how much charge is held in reserve for outages versus made available for daily bill savings, when the system charges and discharges against your time-of-use rate, and what happens when solar is producing. Those settings are the difference between a battery that arbitrages your rate spread and an expensive standby device.

Insist on three things before the crew leaves. A live outage test, meaning they open the main and you watch the house transfer and your intended loads run. A walkthrough of the app, including how to change the backup reserve yourself. And the paperwork: permit sign-off, interconnection authorization, warranty registration, and the model and serial numbers of what was actually installed. Registration is not busywork on every product; on at least one battery we track, part of the warranty term is contingent on registering the unit.

Cash versus lease

The steps above are the same either way. Ownership is what differs, and it should be settled before anything is filed.

If you buy outright in 2026, you own the hardware, any state rebate, and any grid-services income, and you receive no federal tax credit. The Section 25D residential credit expired on December 31, 2025. There is no 30 percent credit for a 2026 cash purchase, in any state, and any quote implying otherwise is wrong. The full picture is in our 2026 battery tax credit guide.

If you lease or sign a power purchase agreement, the provider owns the battery and handles permitting and interconnection as part of the deal. The provider also claims the surviving federal credit, Section 48E, which applies to third-party-owned systems, and may pass some of that value through as a lower payment. You pay monthly for a term, the hardware is not yours, and the contract has transfer and buyout terms that matter when you sell the house. Our zero-down leasing guide covers what that trade actually costs.

Whichever path you take, get the sizing, the permit and interconnection responsibilities, the total delivered price, and the commissioning scope in writing before work starts. Then check the result against your own numbers in the calculator, because the installation is the easy part to get right and the economics are the part that decides whether it was worth doing.