Homeowners considering a photovoltaic installation often ask themselves the question: How do I determine how many solar panels I need? This question is essential because it directly affects the performance and energy efficiency of your system. In this article, our experts explain the steps to follow to best estimate your need for solar panels. However, it is important to consult a professional to get personalized advice and a reliable answer.
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Analysis of your current power consumption
To begin, you need to analyze your current power consumption. You can use your electricity bill for this. It’s better to have an accurate idea of your usage over the course of a year, as it can vary seasonally (air conditioning in summer, heating in winter). Also note peak times and off-peak periods to better calibrate your system.
Monthly payment or annual bill?
If you subscribe to an electricity offer with monthly payments, divide your annual bill by 12 to get an estimate of your monthly usage. If you get a bill every two months, multiply this amount by 6 to calculate your annual usage.
Estimation of potential solar energy production
Once your electricity consumption has been analyzed, it is time to estimate the potential solar energy production of your photovoltaic installation. Several factors influence this estimate:
- Average sunshine in your region: Find out about the average annual sunlight in your geographic area. Maps and data are available online to help you determine this number.
- Type and power of selected solar panel: Solar panels have different yields depending on their technology (mono- or polycrystalline) and their efficiency (15% to 25%).
- Roof Direction: The performance of solar panels also depends on their orientation in relation to the sun. Ideal is a south-facing orientation with an angle of inclination of about 30°.
- Presence of shade: Trees, buildings or other obstructions located near your installation can create shade and reduce the performance of solar panels.
Solar production versus energy demand
With this information, you can estimate the potential solar energy production for your home. Simply multiply the average sunlight by the power and efficiency of the solar panels, then adjust for tilt angle, direction and shade. Then compare this estimate with your current energy needs to determine if a photovoltaic installation is right for your situation.
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Calculation of the number of solar panels required
Now that you have a clear idea of your energy needs and potential solar energy production, it’s time to calculate how many solar panels you’ll need. Here are the steps to follow:
- Determine the total power required: Divide your annual consumption by the estimated solar output (in kWh). This figure is the total power you need to generate with your solar panels.
- Select unit power of solar panels: Solar panels are sold according to their power (usually expressed in peak watts or Wp). The higher the unit power, the more energy each panel can produce.
- Calculate the number of solar panels required: Divide the total power required by the unit power of the selected solar panels. Round up to the next whole number to get the safety margin.
A concrete example:
Let’s imagine that your annual consumption is 4,000 kWh, and the average sunshine in your region allows you to produce 1,200 kWh per year with a 250 Wp solar panel. Here’s how to calculate how many solar panels you’ll need:
- Total power required: 4,000 kWh / 1,200 kWh = 3.33 (rounded up to 3.5)
- Number of solar panels required: 3.5 x 250 Wp = 875 Wp
- Number of solar panels required: 875 Wp / 250 Wp = 3.5 (rounded to 4)
In this example, it is estimated that you will need four 250 Wp solar panels to cover your annual usage.
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Checking available roof space
Before investing in a photovoltaic installation, it is also crucial to check that your roof has the necessary surface area to accommodate the previously calculated solar panels. Typically, a solar panel measures about 1.6 m². Multiply this parameter by the estimated number of solar panels to get the total area required. It is also necessary to take into account the distance between the panels and the obstacles connected with the weight or shape of the roof.
Practical advice:
Use a tape measure and visual cues to help you determine how much space is actually available on your roof. If you are short on space, consider choosing more efficient solar panels (with greater than 20% efficiency) or improving your home’s thermal insulation to reduce your energy needs.
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Call a professional for a tailor-made photovoltaic installation
Calculating solar panel requirements is certainly complicated, but essential to guaranteeing the performance and profitability of your photovoltaic installation. Do not hesitate to contact professionals for personal advice and information on the financial assistance you can benefit from during installation.
Cost of solar installation based on the surface area of the house:
