How to size a photovoltaic installation

When carrying out a photovoltaic installation in our home or business, it will be necessary to know exactly how to size said installation so that, based on our actual consumption, it is as efficient as possible.

How to size a photovoltaic installation

For this , a series of factors must be taken into account , such as, for example, what space we have, what energy consumption we usually make, in what geographical point the property is located, what is the most optimal orientation of the solar panels, etc.

Putting yourself in the hands of a professional in the sector, who advises us on how to size a photovoltaic installation, therefore becomes essential. This will analyze in depth all our needs and the characteristics of our property to recommend the best option before carrying out the installation. The number of solar panels that we install will determine the amount of electrical energy that we can self-consume. In this sense, we recommend you use this solar self-consumption calculator to start evaluating your project.

Below we will analyze the various factors to consider in order to size a photovoltaic installation in the most optimal way.

Previous aspects to take into account before sizing a photovoltaic installation

Before sizing any photovoltaic installation, it will be necessary to consider some essential prior factors:

• energy consumption. A basic aspect prior to determining the size of any solar installation is knowing what our energy consumption is. To calculate it, we must look at how many kWh we consume during a year, discriminating consumption during daylight hours.
• The surface available . We must have enough space to install the number of solar panels that are necessary. Shade areas that limit the power to be installed must be taken into account.
• The orientation and slope of the roof. In the case of carrying out the photovoltaic installation on the roof, we must bear in mind that the more space available we have facing South (South-East, South-West), the installation will be much more usable.

How to calculate the energy consumption of a property

Before sizing a photovoltaic installation, it is necessary to know as exactly as possible how much electricity we are going to need in our property . For this, we must know the kWh that we consume and the hours of the day in which we make those consumptions. These data are essential to analyze how to size a photovoltaic installation and the number of solar panels that will be needed in it, as well as to know what type of installation is the most advisable.

For example, it is not the same to consume the most energy during the day and feed on the direct electricity generated by the photovoltaic panels, than to consume especially when there is no sunlight, in which case we will have to have an energy accumulation system like solar batteries. In the electricity bill we can check the energy we consume (kWh) quickly and easily.

Next, by means of an example, we see how to obtain the data of how much energy the photovoltaic installation will have to provide us based on our annual consumption.

Suppose, for example, that we have an annual consumption during the hours of sunshine of 20,000 kWh/year and that the geographical area in which we find ourselves is the center of the peninsula, whose Peak Sun Hours are 1,600 on average per year. The Peak Sun Hours are the result of the sum of the annual hours in which the solar panels receive 1000 W/m2, that is, they work at maximum theoretical power.

The approximate calculation of solar panels that we need in our installation is carried out as follows:

• Home consumption in sunny hours: 20,000 kWh/year.
• Peak Sun Hours in Madrid: 1,600 HSP.
• Total power of solar panels required: Housing Consumption / HSP = 20,000 / 1600 = 12.5 kWh = 12,500 Watt.

That is, a total power of solar panels of 12,500 Watts will be needed. If the solar panels are, for example, 320 W each, the final calculation would be as follows:

Total power of solar panels / Unitary power of the panel = 39.06 solar panels -> 39 or 40 solar panels would be the ones we need in our installation for our annual energy consumption.

How to dimension the necessary space for the photovoltaic installation

Once we know the number of solar panels that we are going to need, we must check if we have the space or surface necessary to install them. But in order to calculate the total space that we will need for the solar panels , we must ask ourselves the following questions : What type of solar panel are we going to install? since depending on the type the sizes vary; Does the installation area have shadows? since if this is the case those zones cannot be used; What is the orientation of our roof? since a roof facing South has many more hours of daylight than one facing North.

To calculate the available surface for the installation, we must also discount the obstacles that we can find . These can be physical such as a chimney, a window, a vent, etc., or in the form of shadows that limit the power of the solar panel. If it were the case that there is not enough space for the photovoltaic installation, we can always opt for solar panels with greater efficiency , in this way we will need to install less since they generate more energy per square meter.