Inverters explained: lifespan, replacement cost, and what to expect

Solar panels get all the attention. The inverter quietly does the hard work.

It is also the part most likely to need attention first, long before panels “wear out”. If you understand what an inverter does and how it fails, you can compare quotes more confidently and avoid unnecessary extras.

If you want to anchor this to your own roof and location first, start here: Find your postcode

This guide covers:

• what the inverter actually does (in plain English)
• what “normal” lifespan looks like, and why failures happen
• how inverter sizing interacts with export limits and real-world UK output
• what to ask in quotes so you are not sold the wrong solution

Quick answer

Assumptions and variability

• We refer to power (kW), energy (kWh), and panel system size (kWp) (see Glossary).
• This is written for typical UK homes with rooftop solar PV (single-phase supplies are common, but the principles apply broadly).
• Inverter lifespan varies with heat, ventilation, loading, and installation quality, not just brand.
• Export rules can change the practical value of “more inverter” (see DNO, G98/G99, and export caps in the Glossary).
• We avoid pretending there is one universal “right” inverter size. The right answer depends on your roof, your demand pattern, and grid limits.
• For how SolarByPostcode estimates yield and savings by location (and what is and is not included), see: Data sources and methodology

What an inverter actually does (and why you cannot skip it)

Solar panels produce DC electricity. Your home runs on AC electricity.

The inverter sits in the middle and performs three jobs:

1) Convert DC to AC so your home can use it
2) Track the panels’ best operating point as sunlight changes (that is why output rises and falls smoothly on most days)
3) Control safety behaviour: shut down when the grid is off, and respect export limits if configured

If the inverter stops, your panels can be in perfect sunlight and you still get zero usable solar.

That is why inverter quality and installation details matter so much.

The three common inverter setups you will see in UK quotes

1) String inverter (most common)

One box converts the whole array (or two strings) in one place.

Pros: simple, proven, usually the best value
Cons: shading or mismatch on one part of a string can drag the rest down (sometimes)

If you have shade questions, this guide is the right companion:
- Shading and solar panels: when a single tree really does matter

2) Optimisers + central inverter (sometimes justified)

Each panel gets a small device (optimiser) that can help with shade complexity or awkward layouts.

Pros: can improve performance in specific shading/layout cases
Cons: adds parts on the roof (more complexity), often oversold

3) Microinverters (niche, occasionally great)

Each panel gets its own mini inverter.

Pros: very robust against mismatch and shade, modular
Cons: higher cost, more electronics on the roof, not always necessary in the UK

A good installer should be able to explain, in one paragraph, why your roof benefits from extra electronics. If they cannot, assume it is not needed.

How long do inverters last, realistically?

Panels are mostly passive. Inverters are electronics that run hot, switch thousands of times per second, and live for years.

So the honest expectation is:

• Panels: usually keep producing for decades (slow degradation, not sudden failure)
• Inverter: more likely to be your first major component replacement over the system’s life

That is not “bad news”. It is normal engineering. The right mindset is not “avoid replacement at all costs”, but:

• place the inverter somewhere sensible and ventilated
• make sure isolation switches and access are clean
• keep paperwork so a future electrician can swap it without guesswork

If you want the broader “real output” context (why UK roofs do not match brochure numbers), read:
- Why solar panels never hit their rated output in the UK

What actually kills inverters (it is usually boring)

Most inverter trouble is not dramatic. It is predictable stress:

Heat and poor ventilation

Lofts can be brutal in summer. A hot inverter ages faster.

A “cheap” install that sticks the inverter in the hottest, least ventilated corner can cost you later.

High sustained loading

Running close to maximum output for long periods increases thermal stress.

This is one reason inverter sizing needs thought, but it is not the same as “bigger is always better”.

Installation quality

Bad cable terminations, poor isolation switch placement, messy routing, and moisture risks are classic causes of faults.

Grid behaviour and protection trips

Some inverters trip due to grid voltage issues, especially in areas with constrained networks. This is where DNO reality matters.

If you have not read it yet, this guide makes the grid constraints understandable:
- DNO, G98/G99, and export limits: why your inverter may be capped

Inverter sizing: the most misunderstood part of quote comparisons

Quotes often show:

• system size in kWp (panels)
• inverter size in kW (AC output capability)

Many homeowners assume they should match. In practice, they often do not.

Why “panel kWp > inverter kW” can be normal

UK roofs rarely hit nameplate output because of:

• non-perfect orientation and tilt
• temperature losses
• haze and cloud behaviour
• real-world wiring and conversion losses

So a modest mismatch can be a sensible engineering choice, not corner-cutting.

When inverter sizing becomes a problem

It becomes a problem when the quote is hiding a real constraint, such as export caps.

If your export is capped, the limiter can make a bigger inverter mostly irrelevant for export, because you cannot push that power out to the grid anyway.

That is why you should always pair inverter sizing questions with export questions:

• “What export limit are you assuming at my address?”
• “Is that based on G98 or G99?”
• “Is export limiting equipment included, and how is it configured?”

Use this as your quick cross-check:
- How to compare solar quotes without getting misled (neutral, practical)

A postcode reality check: why location changes what “good sizing” feels like

Solar output is not the same everywhere in the UK. That does not just change annual kWh. It changes how often you are near peak output.

A simple way to keep sizing claims honest is to compare a few real locations:

• Higher-yield examples like TR1 (Cornwall) and PL1 (Plymouth)
• Mid-band examples like BS1 (Bristol City of) and LE2 (Leicester)
• Lower-yield northern examples like AB10 (Aberdeen City) and EH1 (City of Edinburgh)

If a quote claims your system will sit near maximum output constantly, sanity-check it against postcode-level expectations:

Find your postcode

“Battery-ready” and hybrid inverters: what that phrase should mean

You will often see phrases like:

• “battery-ready”
• “hybrid inverter”
• “future-proofed”

Sometimes it is real. Sometimes it is vague marketing.

The adult definition of “battery-ready”

A system is meaningfully battery-ready if:

• the inverter can integrate a battery cleanly (or the design makes adding a battery later straightforward)
• there is space, cabling, and a sensible consumer unit arrangement
• monitoring and documentation will still work if you change components later

What you want is clarity, not buzzwords.

Ask:

• “If I add a battery later, what changes?”
• “Will that require replacing the inverter, or can it integrate?”
• “Will the monitoring still work, and who owns the login?”

If you are already thinking about batteries, these guides will sit in the same topic path once published:
- Solar batteries in the UK: who they make sense for (and who should skip them)
- Self-consumption vs export: how SEG actually changes the maths

(For now, you can ground the decision using self-use logic from the sizing cluster:
- Daytime vs evening electricity use in the UK: why self-use matters more than kWp)

How to spot inverter underperformance early (without obsessing)

Most homeowners either never look, or they look too much.

A calm middle ground is:

1) Check that generation exists on a sunny day (not necessarily “maxed”)
2) Notice step-changes: if your system suddenly produces half what it used to on similar days, that is a signal
3) Watch for repeated faults/trips in the app logs

Do not compare your output to your neighbour’s panels. Compare your output to your own history, and to what is plausible for your postcode and season.

If your system is underperforming on overcast days, the explanation is often physics, not a fault:
- Cloud cover vs solar output: what actually happens on overcast UK days

If your inverter fails: what happens in practice?

A failure usually looks like one of these:

• the app shows zero generation despite daylight
• the inverter shows a fault code
• it keeps tripping and restarting

What you do:

1) Check the obvious: isolator switches have not been turned off
2) Look for fault code / warning lights
3) Contact the installer or the inverter manufacturer support (warranty route depends on paperwork)

This is where clean handover documents matter. If you are choosing between quotes, insist on the boring docs:

• MCS certification in the UK: what it guarantees (and what it doesn’t)

The quote questions that protect you (and cost nothing)

Paste these into your quote comparison notes:

• What are the exact inverter model and AC size (kW)?
• Where will it be installed, and how is it ventilated?
• What is the warranty length, and who handles warranty claims?
• What export limit are you assuming at my address (and what is the G98/G99 route)?
• What monitoring platform is used, and will I retain access if I change installer?

If the answers are clean, you are probably dealing with a grown-up installer.

Bottom line

• Inverters are the normal “first replacement” component in many solar systems, and that is fine.
• Most inverter problems are driven by heat, installation quality, and grid behaviour, not by mysterious bad luck.
• Inverter sizing only makes sense when you also understand export limits and realistic UK output.
• The best protection is a sensible install location, clear paperwork, and quotes that state assumptions plainly.

Next reads

• DNO, G98/G99, and export limits: why your inverter may be capped
• Solar monitoring: how to spot underperformance early (without obsessing)
• Why solar panels never hit their rated output (and why that is normal)
• Shading and solar panels: when a single tree really does matter
• How to compare solar quotes in the UK: a numbers-first checklist

Run the calculator for your postcode

Inverter decisions should not be made in a vacuum. They only make sense alongside realistic local generation and your household demand shape.

Run the calculator for your postcode