Homeowners considering solar panels face a key choice: in-roof (integrated) or on-roof systems. On-roof panels sit on top of existing tiles, mounted on frames secured to rafters, making them the most common retrofit option in the UK. In-roof panels replace sections of roof tiles, creating a flush, seamless appearance popular for new builds or major renovations.
Performance differs slightly. On-roof panels benefit from airflow beneath them, keeping them cooler and more efficient. In-roof panels run warmer due to reduced ventilation, leading to 2-5 per cent lower output, according to solar expert Manan Shah of installer Solar4Good. However, newer in-roof designs with ventilated frames are narrowing this gap.
Installation speed and maintenance also vary. On-roof systems can be fitted in one to two days and are easier to access for repairs. In-roof installations are more complex, requiring coordination between roofers and solar installers, but can be integrated seamlessly during a new roof. Both types are weatherproof when installed by an MCS-certified installer.
Cost is a major factor. For a typical 4kW system, in-roof panels cost around £1,000 more than on-roof due to integrated design and extra labour. However, for homeowners replacing a roof, this extra cost may be offset as panels replace tiles, reducing material and labour elsewhere. On-roof systems generally offer better return on investment due to lower upfront cost and slightly higher efficiency.
