Solar inverter types — string, optimisers, microinverters explained

The inverter is the box that turns DC electricity from your panels into AC electricity your house can use. There are three common UK approaches, and the choice meaningfully affects price, shading behaviour, and what you can see on the monitoring app. This guide explains each one, when to pick it, and what to expect to pay extra.

The three approaches

1. String inverter

One single inverter, mounted somewhere convenient (loft, garage, utility room), connected to the panels by DC cabling. The whole array runs as a single "string". If one panel underperforms, the whole string drops to its level.

• Cost: baseline. Roughly £600–£1,200 for a typical domestic inverter (4–6 kWp range).
• Shading behaviour: poor. A single shaded panel drags the whole string output down disproportionately.
• Monitoring: array-level only. You see total generation but not per-panel.
• Brands seen in UK installs: Solis, GoodWe, GivEnergy, Solax.

2. String inverter with DC optimisers

A string inverter, plus a small optimiser unit fitted to the back of every panel. Optimisers do per-panel maximum-power-point tracking, so a shaded panel's reduced output doesn't drag the rest of the string down.

• Cost: roughly £40–£70 extra per panel — adds £400–£900 to a 10–14 panel install.
• Shading behaviour: much better. Each panel runs at its own optimum.
• Monitoring: per-panel — you can see exactly which panel is producing what.
• Safety: DC voltage on the roof drops to safe levels when the inverter is off (rapid shutdown), which simplifies fire-safety responses.
• Brands seen in UK installs: SolarEdge dominates this category.

3. Microinverters

A small inverter on the back of each panel — DC-to-AC happens at the panel itself, so only AC cabling runs back to the consumer unit. No central inverter.

• Cost: roughly £80–£120 extra per panel — adds £1,000–£1,800 to a 10–14 panel install.
• Shading behaviour: as good as or better than optimisers.
• Monitoring: per-panel, very granular.
• Failure mode: distributed. If one microinverter fails, only one panel goes down. But replacement requires getting on the roof.
• Brands seen in UK installs: Enphase dominates; APsystems is the budget alternative.

Which to choose, in plain terms

Choose a string inverter if:

• Your roof has consistent, even sun across the whole array (no chimney, no nearby tree, no overhanging extension)
• You're cost-sensitive and want the lowest upfront price
• You don't care about per-panel monitoring data

Choose optimisers if:

• Your roof has any meaningful shading — chimney, vent pipe, dormer, tree at a certain angle
• You want per-panel monitoring (genuinely useful for spotting underperforming panels years later)
• You want rapid-shutdown safety (helpful but rarely strictly required)
• The extra ~£400–£900 fits the budget

Choose microinverters if:

• Shading is significant or unpredictable
• You want the most resilient distributed setup (one inverter failure = one panel down)
• You don't have wall space for a central inverter
• The extra ~£1,000–£1,800 fits the budget

What about the inverter for batteries?

Adding a solar battery usually means a "hybrid inverter" rather than the basic types above. Hybrid inverters do AC-to-DC for battery charging and DC-to-AC for solar generation — managing both flows in one unit.

• All-in-one hybrid inverters (GivEnergy, Solis, Solax) are popular for new solar + battery installs.
• Battery-only retrofit inverters sit alongside an existing solar inverter, useful when you're adding a battery to a system already running.

If you're spec-ing solar with a battery from day one, ask the installer whether they're proposing one hybrid inverter or two separate units. One unit is simpler; two can be more flexible if you change battery brand later.

A note on warranties

Inverter warranties are typically 10–12 years from the major manufacturers. Microinverters often carry 25-year warranties (matching the panels themselves). Optimisers usually carry 25-year warranties too.

In practice the inverter is the most likely component to need replacing in a 25-year system life. Expect £700–£1,200 for a replacement string inverter at year 10–12.

What to look for in a quote

When comparing solar quotes (see also: eight questions to ask before signing):

1. Confirm the inverter brand and model. "Generic 5kW inverter" is not enough.
2. Check the kVA rating versus your panel kWp. Slight oversizing of panels (e.g. 5kWp panels, 4kVA inverter) is normal and called "DC oversizing" — it's not a problem.
3. If optimisers are quoted, confirm one per panel (not one per string).
4. Check the warranty length — should be 10+ years standard, 25 for premium options.

Related

• How much do solar panels cost in the UK?
• Eight questions to ask before signing a solar quote
• Solar battery storage UK — worth it in 2026?
• Find listed installers covering your postcode