Crystalline panels (poly- - and mono-) give the best results in performance and are currently used for the installation of photovoltaic panels in homes. Amorphous panels are cheaper but are currently in disuse due to their low performance and shorter useful life.
4. Installed capacity
The capacity of the solar panels will indicate the amount of electricity that your domestic installation is capable of producing. Power is usually indicated in units of Wp (peak power in Watts). So the total power for the installation is the sum of the power for all the panels of which it is made up.
Number of panels * power for each panel (Wp) = Installation power (Wp)
For example, an optimal solar panel has a power of 300 Wp. If your installation consists of 6 solar panels you have a total power of 1800 Wp. This power value corresponds to 1800 kWh of electricity annually under theoretical conditions.
It should not be forgotten that the WP value indicated by the manufacturers is measured under optimal conditions of solar radiation (Solar radiation = 1000 W/m2 and Temperature = 25°C). Therefore, to correctly calculate how many panels your house needs, you also need to make a study of both the orientation of the installed surface and the geographical location of your home.
5. Orientation and inclination of the roof
In Spain, the optimal orientation for solar panels is towards the south. This is the orientation that best takes advantage of solar radiation for the production of electricity in a domestic self-consumption installation.
There is no need to worry if you cannot have that exact orientation. In the case of orientations towards the southeast or southwest, the loss of efficiency is only between 1% and 4% which is perfectly acceptable.
In the case of east and west orientations, the fall in efficiency can reach up to 20 or 30%, so it may be necessary to install more solar panels to reach the necessary production power. In the case of north orientations it is important to make a very thorough preliminary study to evaluate whether it is worth installing the panels.
With regard to the inclination, to calculate how many solar panels you need, you will be limited to a certain extent by the structure of the building. Nevertheless, the panels are installed with their own supports so they will be able to have the most suitable inclination.
Generally, the optimal inclination when installing solar panels on a house depends on the latitude of the locality.
Table to calculate the angle of solar panels on a house