Signs of a bad solar installation.

What you can see from the garden.

The ground-level checks aren't the whole picture, but they're free and they catch the worst offenders.

• Panels touching ridges, valleys or chimney flashings. Panels should sit on rails with a minimum 100 mm setback from roof edges and obstacles, so wind uplift can dissipate. Touching panels are an uplift failure waiting to happen.
• Wildly different row alignments. Rails should be set out parallel to the eave with rows on a consistent vertical spacing. Visible kinks or sagging mean the installer didn't snap a line, which usually correlates with cable management inside the loft being equally improvised.
• Visible cables on the roof slope. DC cables should be clipped under the panels with UV-rated cable ties or run inside dedicated trays. Cables draped across slates or pinched under panels degrade in two to three summers and become a fire risk.
• Slates or tiles broken around the mounting hooks. A careful installer dresses the lead flashings around the hook and replaces any tile that cracked during fit. A rushed one leaves hairline cracks that let water in for the next 25 years.
• Bird mesh missing. Below 50° latitude, pigeons will nest under panels within a season. Mesh is cheap (about £8 per linear metre) and should be standard. Its absence is a strong tell that corners were cut.

What's behind the wall.

The cable run from the panels to the inverter is where corners get cut most often, because nobody sees it after handover. The inspection points:

• DC cable routed alongside AC cable in the same conduit. Not compliant with BS 7671 (the UK Wiring Regulations). Induced voltages cause inverter trip alarms and accelerate cable insulation breakdown.
• No separation between DC strings. Strings on different MPPTs should run in separate sleeves. Sharing conduit produces nuisance arc-fault trips and makes fault isolation difficult.
• MC4 connectors crimped with the wrong tool. A standard electrician's crimper is not a PV crimper. Wrong tool, intermittent contact, eventual heat damage. We open one or two and check pull strength on every inspection.
• Cable sizing too small for the run length. Voltage drop on a 25 m run from a 6 kWp array needs 6 mm² minimum; we still find 4 mm² regularly. The system "works" but loses 1-2% generation every year for the lifetime of the install.

The box on the wall tells you a lot.

• Inverter in direct sunlight or an unventilated cupboard. Manufacturer warranties are voided above ambient 40°C. We've seen inverters mounted on south-facing brick walls behind tumble dryers. Expect early failure - and the panel manufacturer won't cover the replacement.
• DC isolator missing or accessible only from a ladder. BS 7671 section 712 requires a readily accessible means of DC isolation. If the firefighter or maintenance engineer can't kill the DC side from ground level, it's non-compliant.
• No labelling. Each isolator, each AC and DC cable, each meter tail should be labelled with its function and the system parameters. Unlabelled installs aren't just untidy - they're a hazard for whoever services the system next.
• Generation meter wired backwards. Reads zero or shows export when generating. We see it once or twice a year. Owner has been on the wrong SEG payment for three years.

If they didn't give you these, ask now.

A compliant install in the UK generates a paper trail. If any of these are missing, the installer either skipped them or never registered the system correctly - and both have consequences for insurance, resale and grid connection.

• Electrical Installation Certificate (EIC). Issued by the electrician on completion. References BS 7671 and lists every circuit, the test results, and the inspector's signature.
• G99 (or G98) approval letter from the DNO. Anything over 3.68 kW per phase needs G99 sign-off from the Distribution Network Operator before commissioning per the Energy Networks Association recommendations. No letter, no legal grid connection.
• Building control notification. A solar PV install is "notifiable work" under Part P of the Building Regulations. Either the installer was a competent-person scheme member who self-certified, or building control was notified directly. Missing means non-compliant.
• Smart Export Guarantee (SEG) registration. You need an MCS certificate to register for SEG payments with most suppliers. If your installer wasn't MCS-registered at the time of install, you cannot retroactively register the system.
• Manufacturer warranty registrations. Panel warranties usually require registration within 90 days. Most installers do this; some forget. Worth checking on day one.

Was the system actually commissioned?

Commissioning is the formal "turn it on and check it works" step. A real commissioning includes string-level IV-curve readings, insulation resistance tests, polarity checks and a stabilisation window with the inverter logging data. A bad install often skips this and just flips the AC breaker.

• No IV-curve report. The IV curve is the fingerprint of your PV system - it shows whether every string is producing its rated voltage and current. Without it, the installer is guessing.
• Monitoring portal never set up. Modern inverters (SolarEdge, Enphase, Fronius, Sigenergy) include free monitoring. If your install came with no login, no app, no portal URL, you have no visibility on whether the system is actually generating.
• No demonstration of the shutdown procedure. In an emergency, you need to know how to isolate AC and DC. A proper handover walks you through this on day one.

The opposite of all of the above.

A well-installed system has parallel rails, clipped cables, a ventilated inverter with labelled isolators within reach, a paper pack containing EIC + G99 + Building Control notice + MCS certificate, an active monitoring login, and a handover where the installer walked you through the shutdown procedure. Nothing exotic - just the basics, done.

The Energy Saving Trust guidance on solar PV and the MCS certified installer database are the obvious starting points if you're choosing an installer. The gov.uk permitted-development guidance covers when planning permission is and isn't needed.

You've got options.

Most issues we find are fixable. The order we work in:

1. 01Document everything visible. Photograph the array, the inverter, the consumer-unit area and the loft cable runs. Date the photos.
2. 02Pull the paperwork. EIC, G99 letter, MCS certificate, Building Control notice. Whatever's missing is the start of the case.
3. 03Get an independent inspection. IV-curve trace, insulation resistance test, thermal imaging on a clear day. Takes us about three hours on site for a domestic system. We inspect third-party installs as a paid service - no obligation to use us for the remediation.
4. 04Decide on the route. Some faults the original installer is obliged to come back and fix under their workmanship warranty. Others are easier to remediate independently. We'll tell you which is which.

If any of this rings true for your system, book a survey and we'll take a look. We're straight about what's wrong, what's fine, and what it'll cost to put right.