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    Solar Inverters UK: String vs Microinverters vs Optimisers

    When each makes sense for your home. The inverter choice affects performance, monitoring, and future battery compatibility.

    Three Types, Three Use Cases

    For a typical UK 3.5 kWp system, string inverters suit ~70% of unshaded homes. The other 30% with shading or complex roofs benefit from optimisers or microinverters.

    String Inverter

    £800–£1,500

    Connects all panels in series to one central unit. Simplest and most affordable. The 'weakest link' effect means one shaded panel reduces the whole string's output.

    Efficiency
    ~98%
    Warranty
    5–12 years (extendable to 20)
    Best For
    Unshaded south-facing roofs, single roof plane, tight budgets
    Avoid If
    Shading, multiple roof faces, or complex layouts — output drops 10–30% from partial shade

    Microinverters

    £2,000–£3,500

    Attached to each panel individually, converting DC to AC at the panel level. Each panel operates independently — maximising output despite variable conditions.

    Efficiency
    ~99%
    Warranty
    10–25 years (matches panel life)
    Best For
    Heavy shading, multiple roof faces/orientations, per-panel monitoring
    Avoid If
    Low budgets with ideal roof — higher upfront cost not justified on clear, unshaded roofs

    Power Optimisers

    £1,500–£2,500

    Attached to each panel like microinverters but optimise DC output before sending to a single central inverter. Best of both worlds — per-panel performance at lower cost than microinverters.

    Efficiency
    ~99%
    Warranty
    12–25 years (optimisers) + 12 years (inverter)
    Best For
    Moderate shading, multi-face roofs, panel-level monitoring without full micro cost
    Avoid If
    Minimal shading — overkill for uniform roofs with no shade issues

    Costs for a typical 3.5 kWp system, excluding VAT and installation. Sources: Which?, MCS installer data.

    Monitoring & Future Battery Compatibility

    Monitoring

    • • String: Basic system-wide monitoring only
    • • Microinverters/Optimisers: Per-panel monitoring via Wi-Fi portal
    • • Panel-level insights are essential for shaded roofs to spot issues early

    Battery Addition

    • • All three types are compatible with battery storage
    • • Optimisers/micro: Easier DC-coupled storage integration
    • • String: May need AC-coupled retrofit (£500+ extra)
    • • Future-proof with optimisers for modular battery additions

    G98 vs G99: Inverter Sizing Rules

    G98 (Most Homes)

    Applies to inverters under 3.68 kW per phase (16A export). Auto-approved for most domestic installs — no DNO application needed.

    G99 (Larger Systems)

    Required for inverters above 3.68 kW per phase. Needs DNO approval (fast-track for under 50 kW). Notification response within 10 days.

    Rule of thumb: Size your inverter to 80–110% of panel capacity. A good installer handles all DNO notifications and flags potential delays.

    Related Guides

    Shaded roof solar solutions →System size guide →

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