Calculadora de Painel Solar
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
Painéis = ⌈consumo_kWh / (sol_h × kW_painel × 30)⌉; área = painéis × 1,7 m²
About this calculator
This calculator estimates how many solar panels are needed to meet the monthly electricity consumption of a home or small business. It considers three main factors: average monthly consumption in kWh, average daily solar irradiation in the region (in peak sun hours), and the nominal power of the chosen panel (in kW). The result is the minimum number of panels (rounded up) and the approximate total area of the system.
The calculation works as follows: divide the monthly consumption by the product of daily sun hours, panel power, and 30 days. The value is rounded up to ensure generation meets consumption. For example, with 300 kWh/month, 5 sun hours, and a 0.33 kW panel, the result is 7 panels. Total area is obtained by multiplying the number of panels by 1.7 m², a typical residential panel area.
Use this tool for initial planning of photovoltaic systems. It is useful for homeowners looking to reduce electricity bills, solar energy investors, or professionals needing a quick estimate. Results help assess required roof space and compare different panel powers. Remember that this is a simplified calculation and does not replace a detailed design by a specialized engineer.
Important considerations: solar irradiation varies greatly with geographic location, roof orientation, and shading. Peak sun hours should be obtained from reliable sources (e.g., INPE or Brazilian Solar Atlas). Actual panel output may be lower than nominal due to losses (temperature, dirt, inverter). It is recommended to add a 10% to 20% safety margin to the calculated number of panels. Always consult a professional for the final project.
Frequently asked questions
How many solar panels do I need for a house with 500 kWh/month consumption?
It depends on local solar irradiation and panel power. For example, with 5 sun hours and 0.33 kW panels, you would need 11 panels (500 / (5 × 0.33 × 30) = 10.1, rounded up to 11).
What does 'peak sun hour' mean?
It is a unit representing the amount of solar energy received in one hour equivalent to 1,000 W/m². Average daily values in Brazil range from 4 to 6 hours, depending on the region.
Does the calculator account for system losses?
No. The calculation is ideal and does not include losses from temperature, dirt, shading, or inverter efficiency. It is recommended to add 10% to 20% to the result to compensate.
What roof area is needed for the panels?
The area is calculated by multiplying the number of panels by 1.7 m² (typical value). For example, 10 panels occupy about 17 m². Check if your roof has enough space and good orientation.
Can I use this result to purchase the system?
Only as an initial reference. Final sizing should be done by an engineer or specialized company, considering actual site data, losses, and technical standards.