Common UK Solar Installation Mistakes to Avoid

Solar installations, when done well, should run for 25 years with minimal issues. When done badly, they cause roof leaks, voided warranties, inflated electricity bills, and failed SEG applications. Most problems are avoidable with the right installer and the right questions asked upfront.

Mistake 1: Skipping the DNO Notification

Every UK solar installation must be notified to the local Distribution Network Operator (DNO) under Engineering Recommendation G98 or G99. Some installers skip this step or delay it — either out of negligence or to speed up the job.

The consequences are serious:

• Your inverter may not be set up correctly for the grid
• Your SEG application can be refused
• Your home insurer may dispute claims related to the system
• Your MCS certificate may be invalid

Always ask your installer to confirm DNO notification as a scheduled step in the installation process, and request written confirmation once it has been submitted.

Mistake 2: No Proper Shading Analysis

A shading analysis should be performed before any system is designed. Relying on a visual inspection alone misses seasonal shading — the chimney that casts no shadow in July may shade two panels every morning in December.

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A credible installer will use modelling software (PVGIS, PVsyst, or Solargis) to quantify shading losses at every month of the year. If your quote contains no shading analysis data, push back.

Mistake 3: Undersizing the Inverter for Future Battery Needs

Many homeowners add a battery 2–3 years after their initial solar installation. If the inverter was not specified with battery readiness in mind, retrofitting can be expensive or impossible without replacing core equipment.

Hybrid inverters — from brands including SolarEdge, GivEnergy, Sungrow, and Huawei — support battery integration from day one. Choosing a hybrid inverter upfront, even without a battery initially, avoids a costly upgrade later.

Mistake 4: Roof Not Surveyed for Structural Integrity

Solar panels add 10–15 kg per square metre to a roof. A competent installer assesses roof condition, rafter spacing, and fixing integrity before installation. On older properties with deteriorating timbers, reinforcement may be needed first.

Signs this step was skipped: no survey visit before the installation date, no mention of roof condition in the quote, installation completed in a single day with no preliminary visit.

Mistake 5: Incorrect Panel Spacing and Ventilation

Panels should be installed with a gap between the panel underside and the roof surface to allow airflow. Without ventilation, panels run hotter, reducing efficiency — solar panels lose approximately 0.35% of output per degree Celsius above 25°C.

On flat roof installations, inter-row spacing should prevent front-row shading of back rows. This spacing is calculated based on tilt angle and latitude and should be documented in the design.

Mistake 6: Not Registering for the Smart Export Guarantee

The SEG is not automatic. Once the system is installed and the MCS certificate issued, you must apply to an SEG-licensed supplier (Octopus, EDF, Ovo, and others) to start receiving export payments. Some homeowners miss this entirely and export electricity for free for months.

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Register for the SEG as soon as you have your MCS installation certificate in hand.

Common Installation Mistakes: Quick Reference