# how big do solar panels need to be: how to choose them correctly?

In this article we will analyze how big do solar panels need to be. The dimensions of photovoltaic panels largely depend on the size of the roof area or the place where we want to install them, as well as our demand for electricity. The type of roof is also important.

## how big do solar panels need to be

Dimensions of photovoltaic panels
Approx. 200 cm x 100 cm x 40 mm
Weight of photovoltaic panels
Approx. 21.00 kg
Number of cells: 72
Power of photovoltaic panels
The power of the photovoltaic module is 380-400 W

Once we have made the decision to obtain cheap and ecological energy produced with the use of solar rays with the help of photovoltaic panels, the moment comes to ask ourselves a few more detailed questions. For the more general ones, i.e. first of all: why do we need photovoltaics? – it is relatively easy to answer. Although you have to bear some investment costs at the beginning, the goal is to save on electricity in the years following the return on investment (usually after 6-8 years). On the other hand, the problem arises when it is necessary to select the appropriate dimensions of photovoltaic panels to, on the one hand, meet the domestic electricity demand, and on the other hand, not to overload the roof on which the panels are installed most often (although this is not a rule).

Therefore, the best answer to the question posed in the title will be: wisely. In practice, it will be the resultant of the size and structure of the surfaces on which they are to be placed, as well as the power that we want to obtain.

## Estimating your home’s energy needs

At the very beginning of the adventure with photovoltaic panels, you need to answer the key question: what is the household’s demand for electricity? According to statistics , a household in the 2 + 2 model (parents plus children) consumes an average of 1,900 kWh per year , and even 2,100 kWh in rural areas . The next step to consider is whether the planned photovoltaic installation is to ultimately cover the entire demand or only part of it. It does not always depend on our decision. It will also be greatly influenced by the surface and construction possibilities of the roof or well-sunny areas on the ground. After determining the annual electricity demandyou can start calculations related to the power of photovoltaic panels we will need and the area they will occupy.

## Dimensions of photovoltaic panels

The dimensions of photovoltaic panels have been gradually standardized over the years – in contrast to the initial period, when their size largely depended on a given manufacturer. Photovoltaic panels consist of photovoltaic cells (60 or 72, depending on the type of equipment). At present, the dimensions of the panels are similar, their width is about 100 cm, and the length is about 165-170 cm (thickness is about 40 mm), with a power of about 280 W.

It is extremely important when checking the dimensions of individual photovoltaic panels to make sure that they are given along with the installation spaces. However, when it comes to weight, an average of a photovoltaic panel weighs approx. 19 kilograms (most often, although it is not a rule). In turn, the efficiency of photovoltaic modules ranges from 15-17 percent, which is a very satisfactory result.

## Roof area and photovoltaic installation

We already have more or less specific dimensions of photovoltaic panels and the annual electricity demand of a given household. Now we can start calculating the roof area that will be needed for the installation. It is not uncommon for photovoltaic modules to cover the entire available roof area, in other cases only a part of it. It is also important whether the panels are placed on special structures on a flat roof, or whether it will be a sloping roof. We have to answer the following questions: How many windows? How are they distributed? With or without “swallows”? etc .. In the first case, you need to keep the appropriate distance between the modules related to the width of the shadow zone. If the installation is on a pitched roof, the modules can be placed very close to each other, filling almost the entire surface of the roof.

The method of calculating the roof area required for the structure is very simple. Assuming that we need a 5 kW photovoltaic generator power, with 102 cm x 165 cm modules and 250 W power, we need about 35 square meters of roof area . We divide the dimensions of the module by the power of the module and multiply it by the power of the generator. So it actually comes out a bit more. Rectangular photovoltaic modules rarely fill the roof perfectly, especially if it is cut with windows or “swallows”.

## The decision is up to us

In the end , the size of a photovoltaic micro-installation will depend on what kind of power we want to get . In the case of small or medium-sized enterprises, they will necessarily occupy a slightly larger area. In the case of households, the demand for electricity is often easily covered by installations mounted on the roof or on the ground. Interestingly, such terrestrial installations are also becoming more and more popular. For example, on farms (sometimes even replacing agricultural activities), but not only. In any case, we can do the preliminary calculations of how much space will be taken up by a possible photovoltaic installation ourselves. It is enough to collect basic data regarding the power, dimensions of the panels and the surface on which they will be installed.