Repairs · Guide
Solar inverter replacement: what to expect
When a solar inverter fails and can’t sensibly be repaired, it is replaced with a new unit matched to your existing panels. An engineer isolates the system, swaps the inverter, commissions it, reconnects the monitoring and notifies your network operator, normally in a single visit.
Mon–Fri 9:00am–5:00pm · Clear written quote before any work starts
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Call 0800 156 0191, Monday to Friday, 9:00am–5:00pm, or send us a message through our contact page.
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England, Wales & Scotland
Warning signs
Signs it needs replacing, not repairing.
Inverters wear out long before panels. The Energy Saving Trust says solar inverters typically need replacing every 10 to 15 years, so many systems from the feed-in tariff years are due one now. For repair versus replacement in more depth, see our inverter repair hub.
Not every fault means a new inverter; a failed fan or a settings problem can often be put right. Replacement is usually the answer when:
- there is an internal board failure, particularly on an older model;
- the model is discontinued and spare parts are no longer available;
- the same fault keeps coming back after repair;
- an error code points to a hardware fault inside the inverter (see inverter error codes).
Some faults start elsewhere. An isolation fault often comes from damp or damaged DC cabling, and a new inverter would report it too. That is why testing comes first. See also how long do solar inverters last?
Make any checks from the ground only: the inverter display, the monitoring app and the fuse board. Don’t go on the roof, open the inverter or touch the DC cables or isolators. SMA’s safety instructions say that when exposed to light, panels generate high DC voltage, present in the DC cables. Panels are live in daylight.
Choosing
Choosing a replacement that fits your system.
- String inverter. One box serves the whole array. It can usually be replaced like for like, or with an equivalent if the original is no longer made.
- Hybrid inverter. A string inverter that can also run a battery, worth considering if you want storage now or later. See hybrid inverters explained and adding a battery to existing solar panels.
- SolarEdge systems with optimisers. SolarEdge’s installation guide says its optimisers don’t start producing power until they are paired with an inverter. In practice, a SolarEdge optimiser system needs a compatible SolarEdge inverter. See solar panel optimisers.
- Microinverters. Each panel has its own small inverter, so a failure usually means replacing the unit behind that panel, which needs safe roof access by an engineer.
Sizing
Sizing, phase and DC voltage.
- Power rating. It should suit the panels’ output. On a feed-in tariff system, a change in rating can affect payments, so check first.
- DC voltage window. Every inverter has a maximum DC input voltage and an operating range. SMA’s technical data, for example, lists a maximum input voltage, an MPP voltage range and a maximum current per input. Your engineer checks the panel strings sit inside those limits.
- Number of inputs. Panels facing two directions are often separate strings, which may need separate inputs.
- Single or three phase. The inverter must match your supply. The ENA’s G98 guide says 16 amps per phase corresponds to 3.68kW on a single-phase supply and 11.04kW on three phase.
On the day
What happens on the day.
- The system is isolated on the AC and DC sides.
- The old inverter is swapped for the new one, usually in the same position.
- The new unit is commissioned and tested, and its output checked.
- Monitoring is reconnected to your Wi-Fi and app.
- A generation meter, if you have one, should still be counting. Photograph the reading before and after, from the display only.
- The network operator is told. The ENA’s G98 guide says your installer must notify the network operator within 28 days of commissioning, and to inform them if you remove or replace your generating unit. If the new inverter, or a battery added with it, takes your total above 16 amps per phase, G99 applies and the network operator generally needs contacting first. See G98 and G99 explained.
Paperwork
Paperwork: who to tell.
- Your FIT supplier, if you’re on the feed-in tariff. Ofgem says you may repair or replace generating equipment without affecting accreditation, as long as the installation still meets the scheme rules, and that you must contact your FIT supplier if the installed capacity goes up or down. Our guide to replacing a feed-in tariff inverter explains the rules in full.
- MCS, if the certificate needs updating. MCS says to ask your original installer first; if they are no longer certified or trading, its helpdesk can make the amendment, for an admin fee. Only the current system owner or their legal representative can request it. For product details, MCS accepts the original installer’s commissioning documents or a signed letter from a currently certified installer on headed paper.
- Your own records. Keep the invoice, serial numbers, commissioning sheet, G98 confirmation and meter photos.
Cost
What affects the cost.
The main factors are:
- the type of replacement: like-for-like string, hybrid, SolarEdge or microinverter;
- the size of the system and the rating needed;
- where the inverter is mounted and how easy it is to reach;
- whether a battery is added at the same time, or G99 approval is needed.
Aftercare
Manufacturer’s cover and disposal.
- Manufacturer’s cover. A new inverter comes with the manufacturer’s warranty. Terms vary by maker and model, so keep the paperwork and check whether the product needs registering.
- Disposal. An old inverter is waste electrical equipment and should be recycled, not put in the household bin. GOV.UK says the WEEE rules aim to reduce electrical waste sent to landfill or incinerated, and that sellers of new household electrical equipment must offer a way to dispose of the old item it replaces. Ask your installer how the old unit will be recycled.
How we help
How we help.
We repair and replace inverters on systems fitted by any installer, across England, Wales and southern Scotland, often within the same week, using our own in-house engineers, never subcontracted. We test first, so you don’t replace an inverter that wasn’t the fault. We work on single and three phase systems, repair and replace SolarEdge and Tigo optimisers, and are a certified Growatt installer. We set up the monitoring before we leave, take the old inverter away for recycling, and handle the G98 or G99 notification. If you’re on the feed-in tariff, we write to your FIT supplier with the old and new inverter details and your meter readings. As an MCS certified installer for solar PV, we can provide the signed installer letter MCS accepts when the product details on a certificate need amending. We are NAPIT registered, TrustMark approved and fully insured, and you get a clear written quote before any work starts.
Questions
The things people ask before they ring.
Not answered here? Call 0800 156 0191, Monday to Friday, 9:00am–5:00pm.
How do I know if my solar inverter needs replacing?
A hardware error code that keeps returning, a blank display in daylight or zero output on a bright day can point to a failed inverter, but some of these start elsewhere. Note any code from the display or app, and have an engineer test the system before you buy a new unit.
Do I need new solar panels when I replace the inverter?
Usually not. The new inverter is matched to your existing panels, and the engineer checks their voltage and current sit within its limits.
Can I replace my inverter with a different brand?
Often, yes, on a standard string system, if the new unit suits your panels, supply and strings. SolarEdge optimiser systems need a compatible SolarEdge inverter for the optimisers to pair with.
Will a new inverter affect my feed-in tariff?
Not if the installation still meets the scheme rules, though you must contact your FIT supplier if the capacity changes. See replacing a feed-in tariff inverter.
Does the network operator need to know about a replacement inverter?
Yes. The ENA’s G98 guide says to inform your network operator if you replace your generating unit; the installer notifies within 28 days of commissioning. Above 16 amps per phase, G99 applies and the network operator should be contacted first.
Ready when you are
Inverter failed or showing a fault?
We’ll call you back to talk it through, and you get a clear written quote before any work starts. Mon–Fri 9:00am–5:00pm.