A commercial solar system is a 25-year asset that needs structured operations and maintenance to deliver the full design lifetime IRR. Done well, a maintenance contract costs £2-£4 per kW per year and protects warranty entitlements, catches degradation before it compounds, and budgets the inverter replacement that almost every system needs around year 12-15. Done badly — or not at all — systems lose 5-15% of expected lifetime generation to undetected faults, soiling and component drift. This page lays out the three SLA tiers we offer (Bronze, Silver, Gold), what each includes, the cleaning economics, the inverter replacement budgeting, and how we take on systems that someone else installed.
Why a maintenance contract matters for the IRR
Commercial solar payback maths assumes the system delivers the modelled annual generation across a 25-year life. In reality, untreated faults compound. A failed string optimiser that is not detected for two years costs the customer 3% of total generation across that string — modest in cash terms but enough to damage IRR. A bird nest under a panel that catches fire costs a panel replacement and an insurance claim. A loose earth bond that goes undetected creates a real safety risk and breaches insurance compliance. None of these are exotic — they happen on routine commercial PV systems regularly. A maintenance contract is the structural defence against compounding small problems into material ones.
The economic case is strong even at the cheapest tier. £200 per year on a 50 kW system buys an annual visit, electrical test, monitoring review and warranty validation. Catching one failed optimiser pays for the contract for a decade. Detecting a 2% performance shortfall in year three prevents the same shortfall accumulating across years four through twenty-five. The maintenance contract is the cheapest insurance product on the asset.
Three SLA tiers
We structure maintenance contracts in three tiers — Bronze, Silver, Gold — sized to the customer's risk appetite and operational requirements. The substantive engineering work is the same on each tier. The differences are visit frequency, response time, cleaning inclusion and warranty management depth.
Bronze tier — annual visit + remote monitoring
The entry tier covers a single annual on-site visit (visual inspection of all panels, mounting and cabling; full electrical test including DC string and AC checks; inverter status review; written report) plus 24/7 cloud monitoring with automated alerts. Response time on faults is best-effort — typically 5-10 working days from alert to on-site attendance. Bronze does not include cleaning or warranty management. Typical pricing: £2/kW/year, minimum £100/year. Bronze is the right tier for healthy modern systems on accessible sites with clean operating environments.
Silver tier — bi-annual visits + cleaning + 48-hour response
Silver adds a second annual visit (so spring and autumn inspections), routine panel cleaning (typically once every 12-24 months on UK sites — see cleaning economics below), a 48-hour fault response SLA, basic warranty management (we file warranty claims with manufacturers on the customer's behalf for product failures), monthly monitoring review with email summary. Typical pricing: £3/kW/year, minimum £180/year. Silver is the standard tier for most mid-market commercial PV (50-500 kW) and what we recommend by default.
Gold tier — quarterly visits + 24-hour response + warranty management + same-day inverter swap
Gold is the operations-critical tier. It includes quarterly on-site visits, 24-hour response SLA on system-down events, same-day or next-day inverter replacement from our local stock, full warranty management (we manage every claim to closure, including replacement units, transport, retrofitting), monthly performance reports with trend analysis, pre-purchased replacement inverters held in stock at year 10 to mitigate obsolescence risk. Typical pricing: £5-£8/kW/year. Gold is the right tier for utility-scale (500 kW+), data-centre and cold-storage applications where any system downtime has direct cost implications, and any site where the customer's internal facilities resource is thin.
What every visit covers
The substantive engineering work on every visit is the same regardless of SLA tier. Specifically: visual inspection of every panel for cracked glass, hot spots, snail trails, vegetation growth, bird nesting; visual inspection of mounting system for corrosion, loose clamps, ballast displacement; visual inspection of all DC and AC cabling for UV degradation, chafing, secure routing; full electrical test (DC string voltages and currents against the baseline established at commissioning, AC voltage and earth integrity, RCD trip test); inverter status review and fault log download; monitoring data review for any underperformance trends or unusual fault states; written report with photographs, electrical test results, performance trend data and any recommended remedial works.
Cleaning economics
Cleaning is the most over-sold and most under-analysed component of UK commercial solar O&M. The basic facts: UK rainfall patterns mean most rooftop solar systems above 10-degree tilt self-clean adequately for routine atmospheric soiling. Measurable performance loss from soiling between cleans is typically 1-3% on UK rooftop systems with normal operating environment. Annual cleaning costs typically £1.50-£3.50 per panel — so a 100 kW system with 250 panels pays £375-£875 per clean.
The cleaning case is strong on specific site types: low-tilt systems (under 10 degrees, typical of flat-roof ballasted installs), agricultural and food-processing sites (organic soiling), coastal sites (salt deposit), busy motorway-adjacent sites (diesel particulate), industrial estates with dusty processes nearby, and any system with measurable bird-droppings concentration. The case is weak on rural, well-tilted, clean-environment sites.
We model cleaning ROI per system. If the predicted performance gain from cleaning exceeds the cleaning cost, we recommend it. If not, we don't. This avoids the typical overselling — annual cleaning regardless of need is a margin-extraction exercise, not maintenance. Typical cleaning intervals: 12 months for soiled urban or industrial sites, 18-24 months for typical commercial roofs, 36+ months for clean rural sites with steep tilt.
Inverter replacement budgeting
Solar panels routinely operate for 25-30 years with linear degradation. Inverters are the shorter-lived component. Standard commercial inverter warranty is 10 years (extendable to 20-25 years on some brands at additional cost — typically £150-£400 per kW for extension). Real-world operating life on Tier 1 commercial inverters (SolarEdge, SMA, Fronius, Huawei, Solis, Sungrow) is typically 12-18 years in normal commercial use, with high-temperature or dust-heavy environments at the lower end.
We budget customers for one inverter replacement around year 12-15 of the system life. Typical 2026 replacement costs are £80-£150 per kW including labour and disposal of the old unit. For a 100 kW system that is £8,000-£15,000 — material money, and one of the few costs that matters in the 25-year DCF beyond the initial capex. Premium Gold-tier maintenance contracts include pre-purchasing replacement inverters at year 10 to lock in current pricing and mitigate the obsolescence risk on inverter models the manufacturer has discontinued. This typically adds £400-£800 per kW to the contract over the relevant period but removes a meaningful piece of long-tail risk.
Warranty management depth
Manufacturers expect the warranty claimant to provide: panel or inverter serial number, evidence of professional installation (MCS certificate, EICR), evidence of routine maintenance (annual visit reports), photographs of the fault, and a written description of the failure mode. A customer attempting to claim independently typically spends 4-8 hours on a single claim. Done by an O&M contractor with established manufacturer relationships, the same claim is processed in 30-60 minutes and resolved in 4-8 weeks rather than 4-8 months.
Silver-tier warranty management means we file the claim and chase it to closure on your behalf, including arranging the replacement unit, retrofit and disposal. Gold-tier extends this to managing the cost of any non-covered remediation works (where the manufacturer rejects the claim and the customer needs an alternative path) and proactive monitoring for early warning signs of impending failure.
Performance reporting
Monthly performance reports show actual generation against the PVSyst-modelled expectation, expressed as a Performance Ratio (PR — typically 78-82% for healthy UK commercial systems). A PR drift downwards is the most reliable early warning of a problem — a single failed optimiser or a soiled string drops PR by a percentage point or two before any obvious symptom appears. Catching the trend at month two rather than month twelve recovers the lost generation. Silver and Gold tiers both include monthly reporting; Bronze provides quarterly summaries.
Taking on third-party installed systems
We take on systems installed by other contractors regularly. The most common scenarios: the original installer has gone out of business (the post-2010 boom and bust left many UK businesses with orphaned systems), the original O&M contract has run out and was not renewed, or the original installer is no longer providing acceptable service. Our process: initial baseline visit (£400-£800 fee, refunded against first year's contract), full electrical test, monitoring re-establishment, documentation reconstruction (we rebuild the as-installed schematic from physical inspection), warranty register validation. After the baseline visit the system goes onto a standard SLA tier on the same pricing as new-build systems. We will not take on systems with obvious safety issues — broken connectors, damaged DC cabling, missing earth bonds — without remediation work first.
Useful authority links
MCS guidance on routine maintenance is at mcscertified.com. The Solar Energy UK trade association publishes O&M guidance at solarenergyuk.org. Ofgem guidance on Smart Export Guarantee compliance: Ofgem SEG.
Related decision pages
For our maintenance service overview see our maintenance service page. For the warranty terms that O&M protects see commercial solar panel warranty. For the commissioning step that establishes baseline performance see solar panel commissioning. For inverter replacement decisions see best commercial solar inverters. For the broader project programme see installation timeline. For the survey and design that establishes the system see commercial solar survey and solar mounting systems. The hub page is commercial solar PV.
Maintenance contract — common questions
How much does a commercial solar maintenance contract cost?
Typical 2026 pricing is £2-£4 per kW per year for routine O&M. A 50 kW SME system pays £100-£200 per year. A 250 kW mid-market system pays £500-£1,000. A 1 MW industrial system pays £2,000-£4,000. Premium tiers with cleaning, faster response SLAs and warranty management run £4-£8/kW/year. Pricing varies by SLA tier, site complexity, regional travel and whether cleaning is included.
Do I need a maintenance contract to keep the warranty valid?
Most panel and inverter manufacturers require evidence of routine maintenance for warranty claims, but they do not specifically require a contract with the original installer. A maintenance log demonstrating annual visual inspection, electrical test and monitoring review is normally sufficient. Where the maintenance log is missing or shows clear neglect, manufacturers can refuse warranty claims. A simple Bronze-tier contract is the cheapest insurance against this risk.
How often does a commercial solar system need cleaning?
UK climate and rainfall patterns mean most commercial solar systems self-clean adequately for routine soiling. Typical cleaning interval is 12-24 months depending on site location. Systems near agricultural sites, dusty industrial estates, busy motorways, coastal salt zones or at low tilt angles (under 10 degrees) need cleaning more frequently. Systems in clean rural areas with at least 15-degree tilt can sometimes go 3-5 years between cleans without measurable performance loss.
How do you handle inverter replacement at end of life?
Standard commercial inverter warranty is 10 years (extendable to 20-25 years on some brands at additional cost). Tier 1 inverter operating life in normal commercial use is typically 12-18 years. We budget customers for one inverter replacement around year 12-15 of the system life — typical replacement cost in 2026 money is £80-£150 per kW. Premium maintenance tiers pre-purchase replacement inverters at year 10 to lock in current pricing and avoid the obsolescence risk on long-discontinued models.
What is the response time on a Gold-tier contract?
Gold-tier SLA is typically 24-hour response on remote diagnostics, same-day or next-day on-site attendance for system-down events, 48-hour replacement of failed inverters from our local stock, and proactive escalation to the manufacturer for any in-warranty claim. Bronze-tier is best-effort — typically 5-10 working days response. Silver sits in the middle at 48-hour response for most events.
Can you maintain a system that someone else installed?
Yes — we take on third-party-installed systems regularly, especially where the original installer has gone out of business (a common issue with the post-2010 boom-and-bust solar market) or where the original O&M contract has run out. We do an initial baseline visit (typical fee £400-£800) covering full site survey, electrical test, monitoring review and documentation reconstruction. After that the system goes onto a standard SLA tier. We will not take on systems with obvious safety issues without remediation works first.
What is included in the annual visit?
A standard annual visit covers visual inspection of every panel and the mounting system (cracked glass, hot spots, corrosion, vegetation growth, bird nesting), full electrical test (DC string voltages and currents against baseline, AC voltage and earth integrity, RCD trip test), inverter status and fault log review, monitoring data review for any underperformance trends, cleaning where SLA includes it, written report with photos and trended performance data. The visit takes a half day on a typical 100 kW site.