Solar Inverter Types Explained: String, Micro, Optimiser & Hybrid

Why The Inverter Matters More Than You Think

The inverter is the box that turns DC electricity from your panels into AC electricity your house and the grid can use. It's also the part most likely to need replacing during your system's lifetime, the part that decides how much you actually generate when conditions aren't perfect, and the most common place where installers quietly upsell or underspec.

Three things ride on the inverter you choose:

• How much electricity you actually get. A basic string inverter on a partly shaded roof can lose 15-30% of total annual generation compared with the same panels on optimisers or microinverters. Over 25 years on a 4 kW system, that's roughly 8,000-15,000 kWh of free electricity left on the table.
• Whether you can add a battery later without ripping the inverter out. Hybrid inverters handle a battery natively. Older non-hybrid string inverters need a separate AC-coupled battery inverter retrofitted, which adds £1,500-£2,500 and another box on the wall.
• How long it lasts. String inverters typically last 10-15 years and need a £600-£1,200 replacement around year 12. Enphase microinverters carry a 25-year warranty, conditional on the system staying connected to the internet through an IQ Gateway. SolarEdge offers 12 years standard, extendable to 20 or 25.

The Four Types You'll Be Quoted

1. Basic string inverter

One box, all your panels wired together in a "string", DC in and AC out. The original technology. Cheap (£500-£1,200 installed), simple, and reliable on a south-facing unshaded roof. The downside is that all panels in a string have to operate at the current of the weakest one, so a single shaded panel drags the rest down with it. Lifespan is 10-15 years.

Buy this if: single south or south-west roof, no shade, no battery plans now or in the next 10 years.

Brands you'll see: Fronius Primo, Solis, GoodWe, Solax, Growatt.

2. String inverter with power optimisers

A string inverter plus a small DC-DC converter (an "optimiser") clipped onto each panel. The optimiser tracks each panel's individual output, so a shaded or under-performing panel doesn't hold back the others. SolarEdge is the dominant brand in the UK and locks you into their optimiser-plus-inverter ecosystem. Tigo optimisers work with most third-party inverters and give you more flexibility.

Adds £500-£1,000 over a basic string inverter on a typical 10-12 panel system. Lifespan of the optimisers themselves is rated at 25 years; the central inverter is still the bottleneck at 12-15 years.

Buy this if: any shading at all, multiple roof faces, or a roof with chimneys or dormers cutting across the panel layout.

Brands you'll see: SolarEdge HD-Wave, SolarEdge Home Hub (the hybrid version), Fronius Primo with Tigo optimisers, Solis with Tigo.

3. Microinverters

One small inverter under each panel. DC is converted to AC right on the roof, so what comes down the cable is already AC. Each panel is a fully independent unit, and there's no central inverter that can fail and take the whole system down. Enphase dominates the residential market in the UK; AP Systems is the budget alternative.

Adds £1,000-£1,500 over a basic string inverter on a typical 4 kW system. The Enphase IQ8 series carries a 25-year UK warranty from the activation date, peak efficiency around 97%, and outputs up to 384W AC per microinverter. The warranty covers England, Scotland and Wales only and is valid only while the system stays permanently connected to the internet through an IQ Gateway, which is itself warranted for five years (enphase.com/en-gb/warranty/uk, checked 18 September 2026). The IQ8HC and IQ8X variants are designed to pair with panels rated 320-540W+, with a small amount of clipping on the brightest summer days.

Buy this if: heavy shade, three or more roof faces, or you specifically want the longest warranty on the market and the safety/independence of no central failure point.

Brands you'll see: Enphase IQ8, IQ8M, IQ8HC, IQ8X. AP Systems DS3 series is the budget alternative.

4. Hybrid string inverter

A string inverter that also handles a battery natively, with one box doing both jobs. In 2026, hybrids are barely more expensive than non-hybrid string inverters at the same AC rating, so most installers will quote you one whether or not you're buying a battery on day one. That's a good thing: it means you can add a battery in five years without ripping out and replacing the inverter.

Hybrids can also be paired with optimisers (SolarEdge Home Hub does this), giving you the best of both worlds.

Buy this if: you're getting a battery now, or you might add one within 10 years (most people will, given the trajectory of battery prices).

Brands you'll see: GivEnergy Gen 3, Fox ESS, Sunsynk Ecco, Fronius Primo GEN24 Plus, SolarEdge Home Hub, Solis hybrid range.

Which One Fits Your Roof?

Three questions, an honest recommendation. This is the same logic an experienced installer would use, written down so you can sanity-check what you're being quoted.

The 3.68 kW Reality That Shapes Every UK Quote

Britain's grid connection rules decide which paperwork route your system takes, and the number that decides it is the inverter's AC output, not the size of the panel array. Get that distinction right and most of the confusion on this subject disappears.

The Energy Networks Association, which writes the rules, puts it plainly: "A generator with a capacity less than 3.68kW/phase then EREC G98 applies. A generator with a capacity greater than 3.68kW/phase then EREC G99 applies." G98 is titled "Requirements for the connection of Fully Type Tested Micro-generators (up to and including 16 A per phase)", and 16 A at 230 V is where the 3.68 kW comes from (energynetworks.org, checked 18 September 2026).

• Up to 3.68 kW of inverter (G98): connect and notify. Your installer fits the system, then notifies your Distribution Network Operator afterwards. There's no application to be approved and nothing for you to do.
• Above 3.68 kW of inverter (G99): the DNO has to agree the connection before the system is commissioned. It can refuse, ask for a network upgrade at your cost, or impose an export limit. There is a fast-track route in G99 for small generation and storage, which most domestic jobs qualify for, so it's usually a formality rather than a saga.

What this means for a typical 4 kW install: nothing to worry about. "4 kW" describes the panels. Almost every 4 kWp array in Britain is wired to a 3.68 kW inverter precisely so it sits under G98, so the job is connect and notify, your installer handles the form, and you are not waiting on anyone's permission. You only get into G99 territory if the inverter is rated above 3.68 kW, which on a domestic job usually means 5 kW or 6 kW.

The way round a larger inverter is "export limiting": the inverter can be sized bigger but software-capped so it never pushes more than 3.68 kW back to the grid, while still delivering full power to your house and battery.

Three practical points:

• If an installer quotes a 5 kW or 6 kW inverter, ask whether they're applying under G99 or relying on export limiting. Both are fine; you just want it in writing, and you want to know who's filling the form in.
• If you have three-phase electricity (rare in UK homes, more common in barn conversions, large detached properties and some new builds), the limit is per phase, so you can fit up to 11.04 kW under G98.
• Export limiting costs almost nothing to enable but does mean surplus generation above the limit is "clipped" and lost. On a 5 kW inverter capped at 3.68 kW you'll typically lose a low single-digit percentage of annual generation, which is usually worth it to stay out of the G99 process.

What "Hybrid" Actually Means In 2026

Five years ago, "hybrid inverter" was an upsell. The hybrid version cost £400-£600 more than the equivalent non-hybrid string inverter, and you only paid the premium if you were certain you wanted a battery.

That's changed. Most major brands now charge a flat price across their range or only a £100-£200 premium for the hybrid variant. GivEnergy's Gen 3 inverter is hybrid by default. Fox ESS's hybrid range is priced within a hair of their non-hybrid models. Fronius's GEN24 Plus is the hybrid version of the Primo, at a small premium.

So if you're being quoted a non-hybrid string inverter in 2026, ask "what would a hybrid version of the same thing cost?". If the answer is less than £300 more, take the hybrid. Battery prices have been falling steadily for years, and most homes that go solar this year will add a battery within a decade. A hybrid means that future upgrade is plug-and-play instead of a fresh install.

Inverter Sizing: Why It's Often Smaller Than Your Panels

You'll often see a quote like "4.5 kWp of panels with a 3.68 kW inverter". This isn't a mistake. It's called DC oversizing and it's the right design.

UK panels almost never produce their rated peak (4.5 kW in this example) because peak rating assumes optimal lab conditions: 1,000 W/m² irradiance, 25°C panel temperature, perfect angle. Real UK conditions (cooler than 25°C in winter, less than 1,000 W/m² most of the year, panels not perfectly aligned with the sun) mean the panels typically deliver 70-85% of their rated peak even at midday in June.

So fitting a smaller inverter (e.g. 3.68 kW for 4.5 kW of panels) means:

• You stay within G98 limits without applying for G99
• You get the full output of the panels for 95-98% of the year
• Only on the very brightest summer days do you "clip" some peak output, losing maybe 1-3% annually
• The inverter runs closer to its rated capacity more of the time, which is its most efficient operating range

SolarEdge Home Hub is rated for up to 200% DC oversizing, meaning a 3.68 kW inverter can have up to 7.36 kWp of panels feeding it. That's an extreme but legitimate design choice if you have the roof space.

What To Look For In Your Quote

A good installer's quote will name the exact inverter make and model. If yours just says "4kW inverter", push back. Specifically ask for:

• Brand and model number. "GivEnergy Gen 3 5.0kW Hybrid" not "5kW hybrid".
• MCS-approved. Confirm by name on the MCS approved product list. Required for Smart Export Guarantee eligibility and any grant funding.
• Warranty length and registration requirements. The headline number is often the registered number, not the number you get by default. Fox ESS is 5 years base and 10 with online registration within 36 months. Sunsynk is 5 base and 10 only if you also fit a Sunsynk battery. Fronius is 5 base, 10 registered, 15 if you pay. Enphase IQ8 is 25 with no registration but needs an always-online IQ Gateway. Ask which one is in your quote.
• Hybrid or non-hybrid. If non-hybrid, what's the cost of upgrading to the hybrid version?
• AC output rating vs DC input. A 3.68 kW AC inverter with 4.5 kWp of panels is fine. A 3.68 kW AC inverter with 7 kWp of panels is aggressive oversizing and you'll clip noticeably more.
• G98 or G99. If above 3.68 kW, who's doing the DNO application?
• Export limiting. If a larger inverter is being export-limited to 3.68 kW, how is that configured (firmware, current transformer)?
• Battery compatibility. If hybrid, which batteries does it work with? Some hybrids only pair with the same brand's batteries (e.g. SolarEdge Home Hub only works with SolarEdge Home Battery, not GivEnergy or Tesla).

What You Don't Need (Save Your Money)

The most common upsells we see in UK quotes:

• Optimisers on a perfectly south-facing unshaded roof. If your roof faces directly south or south-west with no shading, panel-level electronics give you almost no benefit. £500-£1,500 of unnecessary kit. Push back if your installer is selling you SolarEdge here as the default.
• Microinverters when you don't have shade. Microinverters are excellent technology, but their main advantage (panel-level independence) doesn't matter if all your panels are in the same situation. A hybrid string inverter does the same job for £1,000+ less.
• An oversized inverter for "future-proofing". If you're fitting 4 kWp now, you don't need a 6 kW inverter "in case you add panels later". You can almost always add panels to an existing inverter up to 130-150% DC oversizing without changing the inverter. Pay for what you're fitting.
• "Smart" upgrades that don't do anything. All major hybrids come with monitoring apps as standard. You don't need to pay extra for "advanced monitoring" as a line item; it's already there.
• Three-phase upgrade for a single-phase home. Unless you're fitting more than 11 kWp of panels or running serious commercial loads, a three-phase upgrade (which can cost £2,000-£10,000+) is not worth it. Single-phase G99 with export limiting handles almost every realistic UK home install.

The Brands Worth Knowing

Not exhaustive, but the names you'll actually see in UK quotes in 2026:

What we'd avoid for a 2026 install: any non-hybrid model at the same price as the hybrid version, anything not on the MCS approved list (you'll lose Smart Export Guarantee eligibility), and any "no-name" Chinese imports without UK warranty support, however cheap.

For full reviews of each of these brands, with prices, warranty terms, and what each one is genuinely best at, see our best solar inverter UK guide.

Bottom Line

For most UK homes, the inverter decision is simpler than the marketing makes it look:

• Simple south-facing roof, no shade: a hybrid string inverter (Fox ESS or Fronius; GivEnergy is paused while it's in administration). Don't pay extra for optimisers or microinverters.
• Any shading or two roof faces: add power optimisers (SolarEdge or Tigo).
• Heavy shade or three+ roof faces: Enphase microinverters earn the extra cost.
• Battery now or later: always hybrid. The premium over non-hybrid is small and the future-proofing is real.

And in every case: get the brand and model in writing, confirm it's on the MCS approved list, and check what warranty registration requires. The inverter outlives most marriages. Pick one you'll be happy to live with for 12-25 years.