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Find out once and for all which solar energy generation system to choose and save on your monthly electricity bill
A photovoltaic solar energy It is an efficient solution to reduce electricity costs. But how many solar panels are needed to supply the consumption of a residence? Discover how to calculate the ideal number of solar panels for your home in a simple and practical way, according to the video from the E4 Energias Renováveis channel.
Calculation of average daily consumption
To size a solar energy system, the first step is calculate the average daily energy consumption. Let's use an example of a monthly consumption of 800 kWh. Dividing this value by 30, we obtain a daily consumption of approximately 26,67 kWh.
If you don't know your monthly consumption, you can check your electricity bill, where there is usually a history of the last 12 months. Add these values together and divide by 12 to obtain the monthly average.
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Solar irradiation factors
The amount of energy that a solar panel can generate depends on the solar irradiation of the location where it will be installed. For example, a panel in Northeast of Brazil, where the irradiation is more intense, will generate more energy than in the south of the country.
To calculate the energy generated in São Paulo, for example, you can use tools like Google Maps to obtain the Geographical coordinates and then consult the average solar irradiation on the website of the Sérgio de Salvo Brito Reference Center for Solar and Wind Energy (CRESESB). In São Paulo, the average irradiation is 4,64 kWh/m²/day.
Calculation of system power
With daily consumption and average solar irradiation in hand, we can calculate the required system power. Dividing the daily consumption (26,67 kWh) through irradiation (4,64 kWh/m²/day), we obtain a power of 5,75 kWp.
It is important to consider system losses, which may include dirt, deviation from the ideal angle of inclination of the panels, and losses in cables and inverters. A conservative average loss is 25%, which gives us a 75% efficiency. Therefore, the actual system power must be adjusted to 7,67 kWp (5,75 kWp / 0,75).
Choosing a solar panel model
On the market, there are several types of solar panels with different powers and technologies. In this example, we use a panel with power of 665 Wp. To find the number of panels needed, simply divide the total system power (7,67 kWp) by the panel power (665 Wp), resulting in approximately 12 panels.
Therefore, for a consumption of 800 kWh per month in São Paulo, 12 panels of 665 Wp each are needed. This calculation ensures a safety margin, ensuring that the system meets consumption even on days with lower solar incidence.
