Microinverters vs Optimisers vs String Inverters (2026)
Three different technologies for converting and managing solar panel output. Here's how they compare and which makes sense for different UK setups.
The short version
For plug-in solar, you almost certainly want a microinverter — it's the only type designed for socket-connected setups. For rooftop installations, the choice between microinverters, optimisers, and string inverters depends on your roof layout, shading, and budget.
How they compare
| Feature | Microinverter | Power Optimiser | String Inverter |
|---|---|---|---|
| What it does | Converts DC to AC at each panel | Optimises DC at each panel, central inverter converts to AC | Single inverter converts DC to AC for the whole array |
| Plug-in solar? | Yes — designed for it | No | No |
| Panel-level monitoring | Yes | Yes | No — array-level only |
| Shade tolerance | Excellent — each panel works independently | Good — optimisers mitigate panel mismatch | Poor — one shaded panel drags the whole string down |
| Cost per watt | Higher | Medium | Lowest |
| Installation | DIY for plug-in; pro for rooftop | Professional only | Professional only |
| Typical warranty | 5–15 years | 25 years | 5–12 years |
| Best for | Plug-in solar, small arrays, shaded locations | Rooftop arrays with partial shading | Large unshaded arrays on a budget |
Microinverters explained
A microinverter is a small, self-contained inverter attached directly to each solar panel (or shared between two). It converts the panel's DC output to AC right at the source. This means each panel operates independently — if one panel is shaded or underperforming, it doesn't affect the others.
For plug-in solar, microinverters are the standard. Products like the EcoFlow PowerStream are designed to plug directly into a wall socket and include app-based monitoring. You don't need an electrician or any hard wiring.
Plug-in solar advantage: Microinverters are the only inverter type that supports true plug-and-play installation via a standard UK socket.
Power optimisers explained
Power optimisers (like SolarEdge or Tigo) sit on each panel but don't convert DC to AC themselves. Instead, they optimise the DC output from each panel individually, then send it to a central inverter for conversion. This gives you panel-level monitoring and better shade tolerance than a basic string inverter, at a lower cost than full microinverters.
Optimisers are popular for rooftop installations where some panels get partial shading (e.g. from chimneys, dormers, or nearby trees). They're not suitable for plug-in solar.
String inverters explained
A string inverter is the simplest and cheapest option: all your panels connect in series ("a string") to a single central inverter. The inverter handles all the DC-to-AC conversion in one place.
The downside is that the whole string performs at the level of its weakest panel. If one panel is shaded or dirty, it drags down the entire array. String inverters work best for large, unshaded rooftops where all panels get similar exposure throughout the day.
Which should you choose?
Choose a microinverter if…
You want a plug-in solar setup, you have a small system (1–4 panels), or your panels face different directions. Microinverters maximise output per panel and let you monitor each one individually. The EcoFlow PowerStream is the go-to choice in the UK.
Choose optimisers if…
You're getting a professional rooftop installation and your roof has partial shading from chimneys, trees, or neighbouring buildings. SolarEdge and Tigo are the main brands. Expect to pay 10–15% more than a string inverter setup.
Choose a string inverter if…
You have a large, unshaded roof, all panels face the same direction, and you want the lowest upfront cost. GoodWe and SolaX are popular brands with UK installers. Simple, proven technology — just less flexible.
Frequently asked questions
Can I mix microinverters and optimisers?
Not in the same system. They use fundamentally different architectures. Pick one approach and stick with it. For plug-in solar, it's microinverters; for professional installations, discuss the options with your installer based on your specific roof conditions.
Are microinverters more reliable than string inverters?
Microinverters have the advantage of redundancy — if one fails, the rest keep working. String inverters are a single point of failure for the whole array. However, quality string inverters from brands like SMA and Fronius have excellent reliability records. The weakest link is usually the installation quality, not the technology.
Do I need optimisers if my roof has no shade?
Probably not. On an unshaded roof with panels all facing the same direction, a string inverter performs almost identically to an optimiser setup — at a lower cost. Optimisers show their value specifically in partial shading scenarios.
What's MPPT and why does it matter?
MPPT (Maximum Power Point Tracking) is an algorithm that finds the optimal voltage and current combination to extract maximum power from a solar panel. Microinverters and optimisers perform MPPT per panel; string inverters do it per string. Per-panel MPPT means each panel is individually optimised — which matters when panels have different conditions (shade, dirt, ageing).