Before you can determine how many solar panels that you can safely fit on your roof, you need to have the structural frame checked by a professional. If you need new shingles a few years down the road, you should consider new roofing material before beginning installation of any panels. You will also need to determine interference from shade sources which will severely cut the efficiency of any solar panels.
The average solar panel puts out around 300 watts and are about 1.7 square meters. Ten panels will produce approximately 3000 total watts. The panels will have to be installed so they get at least five hours of direct sunlight every day. A single row of ten panels will need close to 40 feet of uninhibited roof space. This means no chimney, vent pipes, or other obstacles on the roof. A small house might not have enough unobstructed room on the roof for this many panels.
Many cities, states, and countries have restrictions on how many solar panels can be installed on a roof. Some electrical companies also limit how many panels can be installed. Before committing to any purchase, you need to fill out all the proper permits and find out what is allowed in your area. The number of panels needed are also determined by the efficiency of the solar panels, the orientation, and the seasons.
The long term weight of solar panels on a roof can lead to shifting and settling of the house. It is possible that leaks can start occurring in valleys and other areas of the roof if the panels aren’t properly installed. Most homes won’t be affected if the installation crew is trained and qualified to install solar panels. It might cost more to have them professionally installed, but future problems from a bad installation job will be avoided.
You will need to determine whether you will use storage batteries or net metering to store extra power. Both systems will allow you to use electricity during non-producing hours. Using net metering will save money over the purchase of storage batteries on a continuous basis.
There are no set ways to determine how many solar panels that you can put on your roof. Many variables will come into play, including available roof area and structural support. Your house will need to be inspected by a professional engineer to help determine the maximum number of panels that can be installed.