The Short Answer
For a home with one roof face and no shade, we'd fit a string inverter, and a hybrid one if you might add a battery. It's one box for the panels, and a battery can go on later without changing it. Add power optimisers if part of the roof is shaded or the panels go on two faces. Microinverters, such as Enphase's IQ8, suit heavy shade or complicated roofs.
Whatever you pick, get the make and model in writing, and expect to replace a string or hybrid inverter at least once in the panels' life: they need replacing after around 12 years.
Which One Fits Your Roof?
1. Does anything shade your roof?
Be honest: even a chimney that shades two panels for two hours a day matters.
2. How many roof faces will you put panels on?
Different orientations or pitches each generate a different amount of power.
3. Battery storage plans?
A hybrid inverter handles a battery without needing a separate box later.
What we'd fit
Hybrid string inverter
An unshaded roof facing one way doesn't need panel-level electronics. A hybrid inverter handles the panels and a battery in one box, so a battery later doesn't mean a new inverter.
Cost: Ask for the hybrid and non-hybrid prices
Get quotes that name the inverter
Ask MCS-certified installers for a written quote with the exact inverter make and model. Don't accept "a 4kW inverter": you want the brand and product name in writing.
The Four Types You'll Be Quoted
| Type | How it works | Suits |
|---|---|---|
| String inverter | All the panels wired in one or two strings to one box on the wall, which turns their DC into AC | One roof face, no shade, no battery plans |
| String inverter with optimisers | A small box on each panel lets it work at its own best output; the strings still go to one inverter | Light shade, or panels on two faces |
| Microinverters | A small inverter under each panel, so AC comes down from the roof and each panel works on its own | Heavy shade, three or more faces |
| Hybrid inverter | A string inverter that also charges and discharges a battery | Anyone with a battery now or likely later; can also take optimisers |
The problem a string inverter has is shade: panels in a string share a current, so one shaded panel holds back the others on its string. Optimisers and microinverters fix that panel by panel. On an open roof facing one way, every panel sees the same sun and there's little to fix.
The 3.68kW Line
The Energy Networks Association, which writes the connection rules, says a generator up to 3.68kW per phase comes under G98, and above that G99. G98 covers fully type-tested micro-generators "up to and including 16 A per phase", which is 3.68kW at 230V. What counts is the inverter's output, not the panels.
- Up to 3.68kW (G98): the installer connects the system and tells your network operator.
- Above 3.68kW (G99): the network operator has to agree the connection first. The installer applies.
- Three-phase supply: the limit is per phase, so about 11.04kW in all.
That's one reason a 4kW array may come with a 3.68kW inverter. Some installers fit a bigger inverter and limit what it exports instead, so ask which your quote assumes.
Why the Inverter Is Often Smaller Than the Panels
A quote for 4.5kWp of panels on a 3.68kW inverter isn't a mistake. Panels are rated in test conditions they rarely meet on a UK roof, so a slightly smaller inverter loses little on the brightest days, keeps the system under G98, and runs nearer its rating the rest of the time. Ask the installer how much output their design expects to lose to this ("clipping"); it should be in the generation estimate.
How Long Inverters Last
The Energy Saving Trust says panels should last 25 years or more, with an inverter replacement after around 12 years. Its maintenance guide puts a replacement at around £800, which is what our calculators allow. For systems in Great Britain activated from 1 August 2026, Enphase's warranty gives its IQ8 microinverters 25 years and its IQ Gateway 5 years. It covers England, Scotland and Wales, and requires the system to be "continuously connected to the internet". Other makers' warranties vary and some depend on registering the product, so ask what yours needs. Our best solar inverter guide compares brands.
What to Check in Your Quote
- Make and model, not "a 4kW inverter".
- Hybrid or not, and if not, what the hybrid version would cost.
- Inverter output against panel size, and how much clipping the design expects.
- G98 or G99, and if it's G99 or export-limited, who applies.
- Warranty length and what it needs: registration, or an internet connection.
- Which batteries it works with, if it's a hybrid.
- The maker's position: GivEnergy Ltd is in administration at Companies House, so a new warranty from it is uncertain.
What You Don't Need
- Optimisers or microinverters on an unshaded roof facing one way, in our view.
- A bigger inverter "in case you add panels later". We'd pay for what you're fitting and ask how many more panels the one quoted can take.
- Paid "advanced monitoring" as an extra line, before checking what the inverter's own app already shows.
Next: how many panels you need and whether a battery pays.
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