Replacing a Solar Inverter UK: Costs, Signs and Your FiT Rights (2026)

The Feed-in Tariff (FiT) scheme ran from April 2010 to April 2019, and at its peak drove hundreds of thousands of UK homes to install solar PV. String inverters — the box on the wall that converts your panels' DC output into usable AC — typically last 10 to 15 years. That means the majority of FiT-era systems are now overdue for, or fast approaching, an inverter replacement. Understanding your costs, your options, and your rights before the unit fails will save you time, money, and unnecessary stress.

How long does a solar inverter last?

The Energy Saving Trust puts the typical lifespan of a string inverter at 10 to 15 years — significantly shorter than the 25-year warranties on the panels themselves, which is why the EST explicitly advises budgeting for at least one replacement over a system's lifetime. Microinverters (one per panel, mounted on the roof) carry manufacturer warranties of 15 to 25 years and tend to outlast string units. Hybrid inverters, which can manage both solar generation and a battery, are generally rated at 15 or more years.

Age is not the only factor. Outdoor installations degrade faster than indoor (loft or garage-mounted) units. Inverters from brands that have since exited the market — ABB/PowerOne Aurora, Samil Power, and early Fronius IG-series — can no longer receive firmware updates or manufacturer support, which shortens their effective life and complicates fault diagnosis. Fronius's SnapINverter range (widely installed 2012–2020) was formally discontinued on 31 December 2025, so newer SnapINverter replacements are no longer available; owners should plan a model upgrade when the current unit fails.

Signs your inverter needs replacing

Most modern inverters use a simple traffic-light LED system: green means normal operation, amber signals a warning, and red indicates a critical fault — the inverter has stopped generating. Beyond the lights, these are the most common signs that replacement (rather than repair) is the right call:

• Generation drop on clear days — if your monitoring shows significantly lower output than the same period last year and shading or soiling doesn't explain it, MPPT degradation inside the inverter is a likely cause.
• Isolation fault (Low Riso) — electrical leakage between the DC circuit and ground. This fault can indicate moisture ingress or deteriorating DC wiring, and should not be ignored — it carries a fire and shock risk.
• Repeated cycling — the inverter shuts down and restarts throughout the day, masking a deeper fault.
• Overheating or continuous fan noise — fan bearing failure becomes common at 8 to 12 years and, if left, leads to internal component failure.
• Physical damage — burn marks, scorching, or moisture inside the casing mean replace rather than repair.
• Age over 12 years — at this point the probability of failure increases substantially. Getting replacement quotes before the unit dies gives you time to compare options rather than accepting the first available quote in an emergency.

For a full list of brand-specific error codes (SMA, Fronius, ABB, Huawei), your installer's service team is the first port of call; the MCS installer search at mcscertified.com/find-an-installer can locate certified technicians by postcode.

Replacement costs

The two variables are hardware and labour. A standard like-for-like swap of a 3–4 kWp string inverter typically runs £650 to £1,100 all-in, combining parts and a 2–4 hour visit from an MCS-certified installer. Within that range, the hardware (inverter unit) accounts for £400–£700 and labour for £200–£400. Factors that push the cost toward the upper end include loft access (add £50–£100), scaffolding for a three-storey property (+£300–£500), and premium brands (SolarEdge, Huawei) that carry a price premium over budget-tier equivalents.

For microinverter systems, replacement hardware costs vary by panel: individual Enphase IQ8-series units run £106–£168 each at current UK retail prices, plus labour and any roof-access costs of £150–£300 per unit for a single replacement. A full 10-panel microinverter set in hardware alone runs £2,000–£3,200.

Should you upgrade to a hybrid inverter?

If your string inverter has failed or is approaching end of life, a like-for-like replacement is not your only option. A hybrid inverter costs roughly £400–£600 more than a standard string inverter when installed — bringing the all-in cost to £1,200–£2,500 — but it gives you the ability to add a battery later without replacing the inverter a second time. If there is any chance you will want home battery storage within the next five to ten years, the extra upfront cost is generally worth it.

The key practical consideration is output rating. If the hybrid inverter you choose exceeds 3.68 kW on a single-phase connection (the threshold for the simplified G98 connect-and-notify route), your installer will need to submit a G99 pre-approval to your Distribution Network Operator before commissioning — and the DNO has up to 45 working days to respond. Plan for this lead time if you are upgrading to a hybrid model with a higher AC rating than your original inverter. Our hybrid inverter buyer guide covers the models available in the UK and what to look for when specifying one.

For the full decision between string, micro and hybrid, see our inverter types guide.

Your FiT accreditation is protected

Homeowners on the FiT scheme sometimes worry that replacing the inverter will void their tariff payments. Ofgem confirmed in December 2021 that replacing generating equipment does not, in itself, result in decommissioning or withdrawal of your FiT accreditation — provided the installation continues to meet scheme rules. You must notify your FiT licensee of any change that increases or decreases your total installed capacity, but a like-for-like swap with no change to system size requires no more than that.

No new MCS installation certificate is required for an inverter replacement. The correct process is for an MCS-certified installer to verify the replacement model is on the MCS Product Directory, then update the product details on the existing certificate. Your installer handles this; the key thing is to use a currently certified company — not necessarily the original installer.

G98 and G99: what notification your installer needs to make

The rules sit with the Energy Networks Association standards, applied by your DNO:

• Same or smaller inverter, AC output ≤3.68 kW (single-phase): no new G98 application required. The installer may commission first and notify the DNO within 28 days (G98 connect-and-notify).
• Larger inverter, still ≤3.68 kW: an updated G98 application is required, submitted post-installation within 28 days.
• Any inverter above 3.68 kW (single-phase) or above 11.04 kW (three-phase): G99 pre-approval is mandatory. The DNO must approve in writing before the inverter is commissioned. Allow 45 working days.
• System previously registered under the legacy EREC G83 standard: replacement triggers a full G98 compliance upgrade. Your installer will manage this.

Planning permission is not required — the permitted development rights under GPDO 2015 Part 14 Class A explicitly include replacement of solar equipment.

What VAT rate applies?

The 0% VAT relief that applies to new solar panel installations (in force from May 2023 to 31 March 2027) covers the installation of qualifying energy-saving materials. HMRC's VAT Notice 708/6 defines a qualifying solar PV system as panels, cabling, control panel and inverter — meaning the inverter is a component of a qualifying installation, not a standalone qualifying item when replaced on its own. The consensus professional view is that an inverter-only replacement is most likely subject to the 5% reduced rate (repair and maintenance on an existing residential energy-saving installation), not 0%. Confirm the rate with your installer before signing off a quote.

Choosing a replacement inverter

The main string inverter brands with active UK support and available spares are SMA, Fronius (GEN24/Argeno/Verto generation, not SnapINverter), SolarEdge, Huawei, and Solis. All carry standard warranties of 5 to 12 years, with extended warranty options up to 20–25 years on registration. Our best solar inverter UK guide compares the leading models on price, warranty, monitoring, and hybrid-readiness. If you are also considering adding a battery at the same time, our solar batteries guide covers whether the economics stack up for a typical FiT-era home.