How to use the calculator
Please enter above the total power of your solar panels in watt (e. g. 10000) and your roof pitch (normally around 30) as well as your deviation in degress from south. If your roof is aligned directly to south the deviation is 0. If your roof is directed 30 degrees more to west or east the deviation is in both cases 30. If your roof is directed to north, then your deviation from south is 180 (degrees).
If the panels lay directly on a flat roof the roof pitch is 0. If you have a normal rooftop the roof pitch is around 30 and if you intend to place the panels on a wall the pitch will be around 90 degrees.
The total wattage of your solar panels is simply calculated by the number of panels multiplied with the peak power of them. So 25 of our 400 watt solar panels would result in a total wattage of 10000 watt.
The results explained
The results will show you a lot of information. The most important value is a expectation of the efficiency in percent.
The efficiency is calculated based on the maximum possible yield under the best circumstances. So if your rooftop is aligned directly to south with a roof pitch around 35 degree you can estimate to generate the maximum possible yield during a year – 100%.
Also the calculator shows you estimations regarding the generated kWh per day, month and year. Additional we show you how high the yield will be in the different seasons based on an european climate (with snow).
The alignment according to the cardinal directions not only has an effect on the efficiency, but also on the time of the peak power. Classically south-facing modules usually achieve their maximum output from 12 to 3 pm. Modules oriented to the southeast generate the most power in the morning and forenoon, while modules oriented to the southwest produce more power in the afternoon. An eastward orientation generates electricity at sunrise and a westward orientation generates electricity at sunset. Accordingly, depending on personal electricity needs, orientation in all directions except north is conceivable.
In addition to the orientation and the roof pitch, shading must be avoided in any case. As soon as a module is shaded, it becomes a consumer and reduces the yield of all other solar modules. Accordingly, the use of several inverters or channels is recommended for an alignment in several cardinal directions in order to exclude such negative effects.
In winter snow could lay on solar panels which will block them from generating electricity, especially if you own a completely flat roof. To avoid problems with snow a roof pitch of at least 40 degrees is recommended.
The best solar setup
So you are asking yourself what is the best setup for your needs?
Normal Rooftop
Well if you need energy the whole day it would be the best to use a system aligned to the south, east and west with a roof pitch of 35 degrees. If your rooftop supports these 3 directions you are able to generate high peaks on morning, lunchtime and evening. For each (of the 3) directions you should use a separate inverter system.
Flat Rooftop
If you are the owner of a flat rooftop you would be able to place all of your panels flat on the rooftop with 0 degrees. Theoretically you would have a high yield in all directions around 87%. This alignment offers you constant energy over the whole day.
In the real world your panels will get dirty and rain could wash them a bit if properly aligned. Therefore we recommend on flat rooftops an alignment of 20 degrees faced to south. This alignment offers you a very high possible yield (97%) per year and performs very well on morning, lunch time and evening.
Shadow
Do not place any solar panels under shadow. Check the future location properly for shadow your house, other houses, trees and other constructions.
If you notice a part of the panels could be affected by shadow connect them to a separate inverter.
However, not only the optimal direction of the sky is important, but also the angle of inclination of the individual solar panels. Optimally, the panels should point perpendicular to the sun. A roof inclination of about 30 degrees is therefore best. Often this cannot be implemented in practice, but the yields are not significantly lower with a deviation than with an optimal orientation. Snow can cause another problem if the angle of inclination is not high enough. On roofs with an angle of at least 30 degrees, the snow usually slides down by itself, so special attention should be paid to a suitable angle here in regions with high snowfall. It is also important to avoid shadows, since even a small shadow will significantly reduce the yields. Due to the complexity of the orientation of a solar system, the consumer is advised to an expert to maximize the efficiency of the photovoltaic system.
