How to install solar panels on the roof?

Installing solar panels on a roof is a multi-step process that calls for careful planning and, for the electrical work, a qualified professional. The steps below cover the process from planning to a working, monitored system.

1. Plan the installation

Start by assessing whether the building and roof are suitable. Check the condition of the roof, the direction it faces, and how much shading there is from trees or other buildings, since these affect how much sunlight the panels will get. At this stage you also estimate how much electricity the household needs and how large a system is needed to cover it, and find out whether a building permit or other official approval is required for the installation.

2. Choose the panels and other equipment

Next, choose the solar panels, the inverter and the mounting system. Panels are compared mainly by power output and efficiency in relation to their surface area, by price, and by the length of the warranty and how well they are expected to withstand Finnish weather. Make sure you have all the necessary materials and tools on hand before starting the installation, including cabling and mounting accessories.

3. Prepare the roof and install the mounting system

Before any panels go up, confirm that the roof structure is in good condition and can carry the extra weight and wind load of the panels; older roofs may need reinforcing. Then install the mounting system the panels will be attached to. Depending on the roof type, this is usually one of:

• Rail system: the most common method, where the panels are attached to rails fixed to the roof structure.
• Roof hook system: used especially on tiled roofs, where hooks are anchored into the roof structures and the panels mounted on top of them.
• Integrated system: the panels are built directly into the roof covering, which can look neater but is more demanding to install.

The mounting system must be sturdy and weatherproof so the panels stay securely in place, and rails or hooks need to be fixed straight and at the correct angle to the roof.

4. Install and connect the panels

Once the mounting system is in place, the panels themselves are attached to it with the fasteners the manufacturer specifies, at the angle and orientation that gives the best exposure to the sun. The panels are then wired together and connected to the inverter, which converts the direct current (DC) the panels produce into the alternating current (AC) used by household appliances. Electrical connections must be made by a qualified electrician and in line with safety regulations.

5. Test and commission the system

After installation, the system is tested to confirm the electrical connections are sound, the panels produce the expected amount of power, and there are no faults. Once testing is complete, the system is switched on and put into use. Many modern systems include remote monitoring, so you can follow production in real time and spot any faults early.