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Solar panel tilt calculation

When we install solar panels, each one of them gives us a number in watts (W) which is the theoretical maximum that it provides in ideal conditions, whic are not always easy to achieve, especially if we do not take into account the calculation of the inclination of the solar panel.

Solar panel tilt calculation

It is something that must be studied very carefully, since it affects the amount of electricity that is going to be generated, so  if we do it correctly, the panel will be very close to its nominal power .

The ideal slope depends on several factors

The best slope for the panels is due to many factors. In addition, sometimes we will have to adapt to the circumstances, knowing that they are not the best to obtain maximum performance.

the season of the year

When calculating the inclination of a solar panel, it is necessary to take into account what season of the year we are in, although there is much to clarify here.

The ideal would be to place the panels with a tracker that would allow them to follow the movement of the sun, as well as being in the best position depending on the time of year.

This is common in solar farms, but it is not feasible in homes, in which placing plates that move following the sunlight is costly and complex, and could also add too much weight to the roof.

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In this way,  during the winter it is best that the plates are at about 60º with respect to the horizontal , as this is how they take advantage of the solar rays that at that moment affect them at an angle.

During the summer the opposite happens , the best inclination is usually around 15º,

Everything changes in spring and summer, where the plates will give more energy if we place them in an intermediate position with respect to summer and winter.

What is the best choice? As a general rule, an inclination that is halfway between the ideal for summer and winter is usually chosen , thus taking advantage of sunlight at all times of the year, although there may be other situations.

We think of the typical summer house that spends the rest of the year empty, in which it would be best to place the plates “in summer configuration”, because that is when we will be in it and we will demand energy (for example, for air conditioning) :

Another situation is that we need a large amount of energy in winter, because we live in a cold area and during the rest of the year our needs fall, so perhaps it is best to install the panels thinking of getting the most out of it in winter.

Our location

We already know that we must choose well the degrees at which we are going to place the plates with respect to the ground, but for this we must take into account the latitude at which we live.

Latitude is the distance that separates us from the equator and in Spain we measure it in degrees north, so we will have to put it in the equation, since living in Galicia has little to do with living in an Andalusian province.

Both places give us different latitudes and, therefore, the incidence of the sun’s rays is also different at all times of the year.

Thus,  the idea is to use this magnitude to be able to use a formula  that helps us choose the best way to install our photovoltaic installation.

the angle of the roof

Another factor to include is the angle of the roof, although this is very easy to correct if we know  how to make a structure of solar panels , with which we can give more or less degrees with respect to the ground.

These structures will allow the plates to be raised or lowered regardless of whether we are going to install them on a roof with a steep slope or on a practicable one that is almost flat with respect to the ground.

We use a formula that helps us choose the degrees of inclination

There are several that we can use so that the inclination is the best,  which will give us the degrees with respect to the horizontal . This is very important to clarify, because with the structures we will have to compensate for the degrees that the roof gives us.

The simplest is to look at the latitude of our location, it is given to us by the mobile if we open  Google Maps , add 15 degrees for winter and subtract 15 during summer.

This is the least complex calculation that can be used if we have a large roof on which we do not mind placing a few more panels, with the idea of ​​compensating for lower efficiency.

If we want to refine more in winter and in summer, we multiply the degrees of latitude by 0.9. In winter we add 29 degrees and in summer we subtract 23.5 from the result. In spring and summer we skip the multiplication and take 2.5 degrees off the latitude.

When we choose the inclination, it may have to be varied, since the panels can shade each other . This would be counterproductive, so it will be necessary to put them at the degrees that are closest to our ideal, always avoiding shadow areas, because that causes the energy they provide to be drastically reduced.

As a general rule, the calculations will have to be more refined the worse the conditions are. This means that a home with a north-facing roof in Asturias will have to calculate to the millimeter, while one in Murcia with a south-facing roof will be able to spend less time choosing the perfect orientation.

Calculating the tilt of a solar panel is very important. Whether it is efficient or not depends on this, so you have to think carefully about what grades you are going to choose, although if you have any doubts,  

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