INTRODUCTION

Why is it important to have the correct distance between solar panels ?

If you have even walked in front of a solar array which is used for pumping water you may have noticed that the pump slows down or stops. This is because the shadow of your body is enough to stop the solar panel working. If you experiment further you will find out that only a small part of a panel has to be obscured to seriously decrease the functioning of the pump. Even the shadow of your head is enough.

If you have rows of panels it is very important that the shadow of one row of panels does not fall on the panel behind. This has most impact in the winter when you need the electricity the most.

If you have limited space to put panels it is important to be able to place them as close as possible to maximise the use of the available space.

How do we calculate the distance between solar panels ?

We have to prepare for the worst case scenario, this is the day of the year when the sun rises lowest in the sky. This day is called the winter solstice. The shortest day of the year. In the northern hemisphere this is around the 21st of December or the 22nd of June in the southern hemisphere. If we have done the calculations correctly the shadow from one row of panels will be just below the bottom of the next row of panels around noon on the winter solstice.

Latitude To do the calculation we need to know the latitude. This is the position on the earth either North or South. For example Madrid Spain is 40.41 - London UK is 51.50 - Houston Texas is 29.76 - Helsinki Finland is 60.16 - Sydney Australia is -33.86. In the northern hemisphere the further north you go the bigger your lattitude will be. The farther north you go the lower the sun will be on the winter solstice and the farther apart the rows of your panels will be.

Height of the Panels The next factor is the height of the panels. We could get confused by using the words width and length. Maybe it is better to speak about panels in portrait or landscape mode. If the panels are in portrait mode we want the length. If they are in landscape mode we want the width. Just measure the panels, we will calculate the actual height off the ground by using trigonometry.

Angle of the Panels The last factor is the panel angle. This is the angle of the panel with the ground. Most panels are between 20º and 45º. The panels are either fixed or variable. You will get more energy from the panels if they are pointing more directly at the sun. Some panels supports are adjustable which means that you can change the angle at different times of the year. In the winter you need a higher angle because the sun is lower in the sky. As the price of panels has decreased there is less incentive to have adjustable panels because it is simpler to just buy more panels than to have the complication of changing the angles. In the future this calculator may become obsolete because everyone will install all the panels flat on the roof or on the ground with almost no tilt thus eliminating the need to avoid shading.

Some considerations I actually made this calculator because I was walking around my barrio in Spain in December. Several houses have solar panels installed with the panels much too close together. The owners of the houses must have paid a lot of money for their installation but it is obvious that in the winter the panels would be generating very little power. So this calculator may raise awareness that the distance between rows can be important and is a factor when deciding where to place solar panels.

You are probably reading this page because you are going to self install solar panels. Before you make any decisions you should also consider laying all you panels flat on the mounting surface with no tilting. This arrangment may be cheaper to mount and more resistant to wind. I am not sure if the amount of power obtained and the price of installation may be better.

Disclaimer You should always be a skeptical of what you see on internet. This calculator was made in good faith and seems to come up with accurate useful results. However, you should always check the results with 2 or 3 sources before you spend money. We cannot accept any responsibility if our figures are wrong.

Please fill in the form below with your own values and then click the button to see the results.