Solar Inverter Replacement Cost — UK Commercial Guide

Solar panels last 25–30+ years. Inverters typically last 10–15. That mismatch means most commercial systems will see at least one inverter replacement during their working life. Plan for it, budget for it, and time it correctly.

Why Inverters Fail Earlier Than Panels

• Heat cycling. Inverters cycle from cold start each morning to peak operating temp by noon. 25 years × 365 cycles = ~9,000 thermal cycles. Capacitors and semiconductors fatigue.
• Capacitors. Electrolytic capacitors are the most common failure component. Typical capacitor life 10–15 years.
• Cooling fan failure. Cooling fans run hours/day and accumulate dust. Bearings and motors fail.
• Firmware obsolescence. Manufacturers stop firmware support typically 12–15 years post-launch. Old firmware = security and grid-code compliance risk.
• Grid code changes. National grid standards (G99, frequency response) update; older inverters become non-compliant.

Signs Your Inverter Needs Replacement

• Output below forecast persistently (after ruling out panel/string issues)
• Frequent grid trips / restart cycles
• Audible whining, grinding, or unusual fan noise
• Temperature alarms in monitoring
• Visible electrolyte leakage on the casing or vents
• Manufacturer end-of-life notification

Replacement Cost Breakdown — UK 2026

• 50kW string inverter: £1,800–£4,000 unit + £400–£800 install = £2,200–£4,800 total
• 100kW string inverter: £3,200–£7,500 unit + £600–£1,200 install = £3,800–£8,700 total
• 250kW commercial inverter: £7,500–£14,000 unit + £1,200–£2,500 install = £8,700–£16,500 total
• 500kW central inverter: £15,000–£28,000 unit + £2,500–£5,000 install = £17,500–£33,000 total
• Microinverters (Enphase): £85–£140 per unit; replace failed units only
• SolarEdge optimisers: £35–£60 per unit; replace failed units only

What's Included in "Install Cost"

• De-energise existing inverter, isolate and lockout DC + AC
• Remove and dispose of old unit (WEEE compliance)
• Mount and wire new unit
• Configure and commission
• G99 / DNO recompliance (notify DNO if grid-tied configuration changes)
• MCS recertification of system
• Updated monitoring + handover documentation

Should I Replace Like-for-Like or Upgrade?

At year 10–15 replacement, the inverter market has typically advanced significantly. Options:

• Like-for-like: Quickest, simplest. New unit drops into existing wiring envelope.
• Upgrade to current-gen string inverter: Better efficiency (98% modern vs 96% 2014-vintage), better monitoring, current grid-code support. Typically same or smaller footprint.
• Migrate to MLPE (SolarEdge / Enphase): Adds per-panel monitoring + fault tolerance. More invasive — adds module-level hardware. Worth it on shaded sites or where O&M visibility matters.
• Repower with battery-ready hybrid inverter: Inverter + battery in one unit. Future-proofs the site for battery addition.

Downtime During Replacement

• String inverter swap: 4–8 hours per inverter. Isolate, swap, recommission. Site can operate at reduced output if multiple inverters present.
• Microinverter swap: Per-unit replacement; rest of system continues.
• Central inverter: 1–3 days per unit including DNO notification.

Frequently Asked Questions

How long do solar inverters last?

String inverters typically last 10–15 years. Microinverters and DC optimisers carry 25-year warranties but have small annual failure rates (~0.05–0.15%). Central inverters last 12–18 years with mid-life capacitor + fan refurb.

How much does commercial solar inverter replacement cost?

UK commercial: £3,000–£8,000 for a 100kW string inverter swap; £8,000–£16,000 for a 250kW commercial inverter; £17,000–£33,000 for a 500kW central inverter.

Can I upgrade to a better inverter when replacing?

Yes — at replacement time, you can upgrade to current-generation string, MLPE, or hybrid (battery-ready) inverters. The marginal cost is typically modest vs like-for-like, and benefits include better efficiency, monitoring, and grid-code compliance.

Will inverter replacement disrupt my solar generation?

Yes, briefly. String inverter swap takes 4–8 hours per unit. On systems with multiple inverters, the site continues at reduced output during the swap. Microinverter replacement only affects the single panel.

Does inverter replacement affect MCS or SEG?

Yes — the system needs MCS recertification after major component replacement. We handle this as standard. SEG is not interrupted provided MCS recertification is timely.

Related Guides

• O&M contract
• Solar maintenance UK
• String vs microinverter
• Solar monitoring