Solar inverter replacement: signs, timing and options

Replace a solar inverter once a professional has confirmed the fault and you’ve compared repair, warranty support and a compatible replacement. Age alone doesn’t mean it has failed. Before you approve work, get the diagnosis, any costs the warranty leaves to you, the compatibility check and the permit and utility steps in writing.^1,2

How long does a solar inverter last?

String inverters usually last 10 to 15 years, according to the U.S. Department of Energy, and may need replacing during the life of the panels. Microinverters tend to last about as long as the panels do.¹ Those are planning ranges, not deadlines for your equipment.

Your system and your inverter can be different ages, so find the install date and any replacement record. The type matters for what a failure costs you in lost output:

Panel optimizers add a third arrangement, so confirm exactly what’s on your roof before you compare quotes.²

What are the warning signs of a failing inverter?

Repeated fault messages, a shutdown or a lasting drop in production all justify a professional look, but none of them proves the inverter is the problem. Maryland’s consumer guide, published in January 2018, says a complete loss of output in daylight can come from blown fuses, wiring issues, breakers or ground faults.³

The same guide notes that voltages inside an inverter can reach 600 volts DC, so it leaves troubleshooting to a qualified solar professional.³ What you can do is keep records:

• Dated monitoring screenshots, with the date and time the output dropped.
• The exact message or light pattern on the display, read from where you normally stand.
• Whether one panel, a group or the whole array is affected.

Not every shutdown is a hardware failure. DOE’s inverter explainer says small residential inverters are built to ride through minor voltage or frequency swings, and to disconnect and shut down if a disruption is large or lasts a long time.⁴ For light codes and app errors, check the manufacturer’s own support pages. Our guides on a system that isn’t producing and monitoring that’s gone offline cover the checks that come first.

Say your app shows zero output for three sunny days and the inverter display shows a fault code. With the screenshots and the code in hand, a service provider has a place to start. “It stopped working” gives them nothing.

Repair or replace?

For string inverters and microinverters, repair usually means replacement. NREL’s maintenance guide, written mainly with larger systems in mind, says they generally require replacement of the whole unit, unlike large central inverters, whose subsystems can be repaired one at a time.² So the real questions are which replacement, under whose warranty, and what else has to change to fit it.

NREL’s system-review checklist asks whether the repair-or-replace call rests on parts availability, size, type and cost.² Apply the same test to any proposal. The table below assumes a provider has confirmed an inverter fault and the panels are in good shape.

If you don’t own the equipment, read the ownership agreement before anyone touches it.¹

Roof-mounted microinverters add a wrinkle. Maryland’s 2018 guide flags the labor of removing and replacing panels to reach a failed unit as a cost concern.³ Find out who handles that access and who documents the roof’s condition before and after.

How much does an inverter replacement cost?

None of the federal or state guides cited here gives a current Maryland price for swapping one residential inverter, and contractor prices vary too much to quote responsibly. What exists is old: a 2018 table in an NREL maintenance guide, written mainly for larger systems, that models 20-year replacement costs.²

That table assumes a lifetime replacement cost of $0.25 per watt for string inverters (estimated at twice the factory price) and $0.40 per watt for microinverters.² These are modeled 20-year totals from a 2018 benchmark, not the price of a single swap, so use them only as a sense of scale.

Scope is the better thing to compare. Two proposals with the same hardware can differ a lot in labor, roof access and electrical work, so line them up item by item:

A hardware-only price next to a full-scope quote isn’t a comparison. The lower number may just be the smaller job, so get the same list from every provider, with a reason attached to each added component.

What should an inverter warranty cover?

Read the warranty for your installed model before you approve anything, and get its issuer to confirm coverage in writing. Maryland’s 2018 consumer guide says most inverters carry a standard warranty of at least 10 years, and NREL’s 2018 guide says 10-year terms are common, with 20-year extended plans becoming more so.^3,2 Neither is a promise about your unit.

The guide adds that longer terms usually cost extra and, in most cases, can be bought directly from the manufacturer.³ A warranty’s value comes down to labor, timing and conditions:

• Labor. NREL, writing about modules, warns that a manufacturer’s warranty can cover a replacement unit without the labor to remove, ship and reinstall it.² The same question applies to an inverter, so get the answer in writing.
• Timing. NREL says some string inverter manufacturers can take up to about a month to send a warranty replacement.² Find out how long your system will sit idle.
• Conditions. NREL also notes that inadequate ventilation can void an inverter warranty.²

It also separates component warranties from installation workmanship coverage, and says an installation warranty of at least five years is generally accepted.³ Those are 2018 descriptions, so rely on your contract and the issuer’s written decision. Gather the model and serial number, the purchase record and any replacement history before you call. For the wider picture, see solar panel warranties explained.

Does a battery change the inverter decision?

Yes, if a battery is on your list, settle that before you pick a replacement. A battery is commonly added through its own inverter, leaving the solar inverter alone. NREL’s 2020 resilience report shows this AC-coupled arrangement as the common retrofit design, while DC-coupled systems are more common in new builds.⁵

Solar panels produce direct current (DC) and homes run on alternating current (AC). In an AC-coupled setup the battery connects on the AC side. In a DC-coupled setup the panels and battery share an inverter on the DC side.^4,5 Have the designer confirm compatibility with your exact panels, electronics and battery.

A standard grid-tied system shuts down in an outage. Backup needs a design that isolates the house from the grid and manages the power.⁵ DOE says solar-plus-battery systems can run without the grid only if they’re designed to.⁴ The battery’s energy and power ratings cap what it can run, so request a list of the backup circuits and their limits. More is in adding a battery to existing solar. Soleil Energy’s battery storage page describes adding storage to systems already on the roof.⁶

What permits and utility approval does an inverter swap need?

Start with your permit office and your utility before work begins, because neither will necessarily treat an inverter swap as routine. Two parts of the Code of Maryland Regulations (COMAR) 20.50.09.06 matter for inverters, and both concern interconnection rather than building permits.⁷

• Paragraph D: once an interconnection request is complete, a material modification other than a minor equipment modification needs a new request unless the utility agrees in writing.
• Paragraph O: after January 1, 2024, new interconnection requests must use a smart inverter with a utility-required settings profile. A facility may replace an existing inverter with a similar spare purchased before that date, and the paragraph says this requirement doesn’t apply to replacements under manufacturer warranty.

Neither paragraph says whether a specific swap counts as a “minor equipment modification,” so have the utility classify your work in writing. According to the PSC, newly interconnected smart inverters must use a statewide standard, utility default or site-specific settings profile, so have your provider confirm the right one with Pepco, Baltimore Gas and Electric, or your own utility.⁸

The chapter is also being rewritten. The PSC proposed amendments to COMAR 20.50.09 in the Maryland Register on September 18, 2026, leaving paragraphs D and O(1) through (11) unchanged, and took comments through October 19.⁹ As of October 25, 2026, the newest Register issue available (October 16) still listed the chapter among pending proposals, not adopted ones, so check the PSC page for the version in force.¹⁰

On the county side, Montgomery County’s Department of Permitting Services separates the rooftop solar building approval, which its eSolar process covers, from the electrical permit.¹¹ That page is about new installations and doesn’t settle an inverter-only swap, so confirm with your own permit office whether the job needs a permit, a revision or an inspection. Our Montgomery County permit guide walks through the local process, and Pepco’s interconnection and permission to operate covers the utility side.

Before you approve work, get written answers to five questions:

1. Diagnosis: What evidence shows the inverter is at fault and rules out another problem?
2. Equipment: What exact replacement is proposed, and what compatibility checks come with it?
3. Approvals: Who confirms permit requirements, inspection, utility notice and permission to operate (PTO)?
4. Billing: Does the scope trigger a new interconnection agreement or change how your system is billed and credited?
5. Handover: Who supplies the new equipment record, commissioning results, monitoring access and warranty paperwork?

Where to start if your inverter has stopped working

Record the symptoms, find your warranty and install date, and don’t let anyone price hardware alone. Soleil Energy’s monitoring and maintenance service includes inverter fault diagnosis and repair, including on systems another company installed.¹² A system assessment would show what’s serviceable.

Request a system assessment or call (301) 953-4140.

This guide is general information, not legal, tax, or financial advice.

Sources (12)

1. U.S. Department of Energy, A Consumer’s Guide to Buying a House with Solar Panels, published April 19, 2023, page modified April 26, 2023; read October 25, 2026. Used for lifespan and equipment-type guidance only. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷

2. National Renewable Energy Laboratory and partners, Best Practices for Operation and Maintenance of Photovoltaic and Energy Storage Systems, third edition, December 2018, sections 5.2, 5.9.3 and 10.1, Table 1 (replacement costs from Feldman et al., 2018) and the warranty discussion; PDF read October 25, 2026. The cost figures are 2018 planning assumptions. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰

3. Maryland Energy Administration and Clean Energy States Alliance, A Maryland Consumer’s Guide to Solar, January 2018, troubleshooting and warranties sections (pages 40-43); PDF read October 25, 2026. Used for technical and document-review guidance only. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶

4. U.S. Department of Energy, Solar Integration: Inverters and Grid Services Basics, published November 7, 2019, page modified March 31, 2025; read October 25, 2026. ↩ ↩² ↩³

5. National Renewable Energy Laboratory, Will Solar Panels Help When the Power Goes Out? Planning for PV Resilience, March 2020, printed pages 3-4 and Figure 4; PDF read October 25, 2026. ↩ ↩² ↩³

6. Soleil Energy, Battery storage, current page, read October 25, 2026. ↩

7. Code of Maryland Regulations 20.50.09.06, paragraphs D and O, Library of Maryland Regulations, current text, read October 25, 2026. ↩

8. Maryland Public Service Commission, Small Generator Interconnection, Smart Inverter Standards section, current page, read October 25, 2026. ↩

9. Maryland Register, volume 53, issue 19, September 18, 2026, proposed action 26-143-P (regulation .06, public comment section); read October 25, 2026. A proposal, not an adopted rule. ↩

10. Maryland Register, volume 53, issue 21, October 16, 2026, table of pending proposals (COMAR 20.50.09, 53:19 Md. R. 953); read October 25, 2026. ↩

11. Montgomery County Department of Permitting Services, eSolar Residential Rooftop Solar Panels, current page, read October 25, 2026. ↩

12. Soleil Energy, Monitoring and maintenance, current page, read October 25, 2026. ↩