A solar inverter replacement is the one major job most PV systems will need. The inverter typically lasts 10 to 15 years, while the panels run for 25 or more (Simple Green Energy, 2026). It is the hardest-working component and the first to wear out. Planning for the swap is part of owning solar, not a sign something has gone wrong.
For a UK homeowner the questions are practical. How do I know it is failing? Do I repair or replace? What will it cost, and does the grid operator need telling? A typical domestic replacement runs about £500 to £1,500 installed (GreenMatch, 2025). A like-for-like swap is straightforward. Change the export rating, though, and you change what the DNO expects. That is where this job needs care.
Key Takeaways
- Inverters last about 10 to 15 years, far less than the panels, so most systems need at least one replacement (Simple Green Energy, 2026).
- Lifespan varies by type: string 10 to 15 years, hybrid 12 to 15, microinverters 20 to 25 (Solar Panels Network, 2026).
- Warning signs include zero output on sunny days, error codes, repeated restarts, overheating and generation well below previous years (Solar Panels Network, 2026).
- A typical UK replacement costs £500 to £1,500 installed, more for hybrid upgrades (GreenMatch, 2025).
- Heat is the main enemy of inverter life, so a cool, ventilated location matters as much as the brand (Solar Repair Centre, 2026).
Knowing when to replace a solar inverter
Replace a solar inverter when repair stops being reliable or economic, which usually arrives around the 10 to 15 year mark (Simple Green Energy, 2026). The trigger is not age alone. It is a pattern of faults, falling output or repeated shutdowns that no longer clear with a reset or a single repair.
There is a judgement call here that a good installer makes with the owner. A one-off fault under warranty is a repair. A unit that keeps tripping, or shows heat damage, is a replacement. Repeated call-outs on an ageing inverter usually cost more than a clean swap for a current model.
Environment shortens or extends that timeline. Heat is the primary enemy. An inverter baking on a south wall, or in an unventilated cupboard, ages faster than one in a cool, shaded spot (Solar Repair Centre, 2026). Where the unit sits is worth checking during routine solar panel maintenance, long before it fails.
How long do solar inverters last?
Solar inverter lifespan depends on the type. String inverters last 10 to 15 years, some failing at 8 and some running past 20. Hybrid inverters manage 12 to 15. Microinverters reach 20 to 25 (Solar Panels Network, 2026). Matching the replacement to the original type keeps the job simple and the wiring familiar.
The table below sets out typical lifespan and UK replacement cost by inverter type. Prices are installed estimates and move with brand, system size and site access, so treat them as a planning range rather than a fixed quote for any one job.
- String inverter: 10 to 15 years, around £500 to £1,200 replaced
- SolarEdge string plus optimisers: similar lifespan, around £800 to £1,800
- Microinverters, such as Enphase: 20 to 25 years, around £150 to £350 per unit
- Hybrid inverter: 12 to 15 years, around £1,000 to £2,500 to upgrade
- Typical domestic replacement, all in: around £500 to £1,500 installed
Type also shapes the failure pattern. One string inverter is a single point of failure for the whole array. By contrast, microinverters fail one at a time and cost less each to swap. That trade-off, between a cheap central unit and distributed resilience, is worth weighing whenever a replacement is on the table.
What are the common signs and fault codes of a failing inverter?
The clearest sign is zero output on a sunny day, usually alongside a red or amber warning light and an error code on the display or app (Solar Panels Network, 2026). Repeated shutdowns and restarts, unusual fan noise, overheating and generation well below previous years all point the same way.
Fault codes vary by manufacturer, but the families are consistent. An isolation or Riso fault flags a drop in insulation resistance. It often comes from moisture ingress or a damaged DC cable. A grid or AC fault means the inverter saw voltage or frequency outside its limits and disconnected to stay compliant. An over-temperature code points to poor ventilation or a failing fan.
- Isolation or Riso fault: low insulation resistance, often moisture or cable damage on the DC side
- Grid or AC fault: mains voltage or frequency out of range, so the inverter disconnects to protect itself
- Over-temperature: blocked ventilation, high ambient heat or a failing cooling fan
- No output or no display: total failure, tripped protection, or loss of DC or AC supply
Not every code means replacement. A grid fault can be the network rather than the inverter, and an isolation fault can be a wet connector that dries out. Log the code, note the conditions, and diagnose before condemning the unit. A pattern of the same fault returning after repair is the signal that the inverter itself is done.
Should you repair or replace a solar inverter?
Repair makes sense when the inverter is young, in warranty, and the fault is a known, fixable part. A fan or a single component is worth fixing. Replace when it is out of warranty, the fault keeps returning, or spares are scarce. Also replace when another repair approaches the price of a new unit. Age, fault history and warranty status decide it together.
Parts availability quietly drives many decisions. Older models can be discontinued. A repair then means hunting for used boards while the system sits dead and generation is lost. A current replacement restores output quickly, often improves efficiency and monitoring, and resets the warranty clock. For a unit past 12 years, replacement is usually the lower-risk choice.
A replacement is also a natural moment to reconsider the system. If the household is thinking about storage, swapping a straight string inverter for a hybrid inverter can prepare the ground for a retrofit battery later. That only makes sense if the numbers stack up, but the inverter swap is the cheapest time to make the change.
How much does solar inverter replacement cost in the UK?
A typical UK domestic inverter replacement costs about £500 to £1,500 installed, with hybrid upgrades reaching £1,000 to £2,500 (Upvolt Energy, 2026). A standard string unit sits at the lower end, while systems with optimisers or a move to hybrid cost more for the hardware and the extra commissioning work.
The quote should separate the unit, the labour and any grid work. A like-for-like string swap is a few hours on site. A change of type, or an upgrade that touches export capacity, adds a DNO notification and more commissioning time. Ask what is included, because the cheapest headline price sometimes leaves out the paperwork that the job legally needs.
One cost is easy to forget: lost generation while the system is down. Sourcing an obscure part can leave an array offline for weeks. That is a real argument for replacing a long-discontinued inverter promptly rather than chasing a marginal repair, especially heading into the brighter months when the array should be earning its keep.
How to replace a solar inverter, step by step
Replacing an inverter is qualified electrical work, not a DIY job, and the sequence protects both the installer and the grid connection. The core steps are isolate, remove, assess the grid rules, fit, commission and notify. Getting the grid assessment right, before touching a spanner, is what separates a compliant swap from an expensive mistake.
- Isolate safely. Shut down and lock off the AC and DC isolators, then confirm dead before disconnecting the old unit.
- Check the export rating first. The determining factor is maximum export capacity, not panel or battery size (Solar Tech Support, 2026). A true like-for-like swap keeps the same rating.
- Match the grid application to the change. A like-for-like replacement may only need a G98 variation, but raising export above 3.68 kW on single phase requires a G99 application before commissioning (Solar Energy Concepts, 2026).
- Fit and wire the new unit. Follow the manufacturer settings for the UK grid code, including the correct protection settings and any required relay.
- Commission and document. Test, record the commissioning data, update the monitoring, and hand the owner the paperwork for their records and warranty.
Do not assume the old notification still covers the new unit. The installer must reassess the revised system against current G98 and G99 requirements rather than relying on the original approval (Solar Energy Concepts, 2026). Where protection settings or a G99 relay are involved, get them right at commissioning, because a later correction means another site visit.
Frequently asked questions
How long does a solar inverter last?
Most inverters last 10 to 15 years, though it varies by type. String inverters run 10 to 15 years, hybrids 12 to 15, and microinverters 20 to 25 (Solar Panels Network, 2026). Heat is the biggest factor, so a cool, ventilated location extends life while a hot, sealed spot shortens it. Expect at least one replacement over a panel's lifetime.
What are the signs a solar inverter needs replacing?
Watch for zero output on sunny days, persistent error codes, repeated shutdowns and restarts, unusual fan noise, overheating, or generation well below previous years. A single fault may just need a repair. The same fault returning after a fix, or several symptoms together on an older unit, is the sign that replacement is the sensible next step.
Do I need to tell the DNO when I replace my inverter?
Usually yes. A like-for-like swap that keeps the same export capacity may only need a G98 variation, but any change that raises export above the 3.68 kW single-phase threshold needs a G99 application before commissioning (Solar Energy Concepts, 2026). Your installer assesses the revised system against current rules rather than assuming the old approval still applies.
Can I replace a string inverter with a hybrid one?
Yes, and it is a common upgrade when adding storage. The catch is export capacity: a larger hybrid can push export above the G98 limit and trigger a G99 application. Treat it as a chance to prepare for a retrofit battery, but only if the economics work. Your installer should confirm the grid application before ordering the unit.
How much does it cost to replace a solar inverter in the UK?
Around £500 to £1,500 installed for a standard replacement, and £1,000 to £2,500 for a hybrid upgrade (Upvolt Energy, 2026). The final price depends on the inverter type, system size, site access and any grid work. Ask for the unit, labour and DNO steps to be itemised so you can compare quotes fairly rather than on the headline figure alone.
For installers, inverter replacement is steady, high-value work that rewards a clean process: diagnose properly, quote transparently, and get the grid application right the first time. Standardising that sequence across a team is exactly the kind of workflow Reonic's tools are built to support.
