Solar Panel Calculator
Estimate how many solar panels (Wp) you need to offset monthly electricity consumption (kWh) of a home. Everything in your browser.
Sizing a residential PV system
PV systems are sized from the monthly consumption in kWh. A typical 2024-2026 panel delivers 550-600 Wp (Watt-peak, measured at Standard Test Conditions). Brazil's average insolation is 4.5-5.5 kWh/m²/day, reaching 6+ in the Northeast sertão. A 1 kWp system generates roughly 110-150 kWh/month depending on the region. The simplified formula is panels = monthly_kWh / (Wp · peak_sun_hours · 30 · efficiency). Example: 400 kWh/month, 600 Wp panels, 5 peak-sun hours/day, 80% system efficiency → 400 / (0.6 · 5 · 30 · 0.8) ≈ 5.6 → 6 panels. Brazilian net metering is regulated by Law 14,300/2022 (the GD legal framework), with energy credits valid for 60 months. Residential payback is typically 4-7 years. Pick an on-grid inverter for systems tied to the utility or off-grid with batteries for autonomy.
Applications
Residential bill reduction, commercial and rural installations, financing pre-quotes via Solfácil/Volt and similar platforms, dimensioning for self-consumption, sizing for ESG and corporate sustainability reports.
How many solar panels you need
Every solar energy project starts with the same question: how many panels will cover the electricity bill? The estimate comes from here, based on your monthly consumption in kWh and the panels' power in Wp.
The tool cross-references how much electricity you use per month with each panel's expected generation, then points to how many you'd need to zero out, or at least sharply cut, what you draw from the grid. It works as a solid starting point for sizing the project and the investment before you even call an installer.
It runs in the browser and counts as an initial estimate. Actual generation depends on location, roof tilt and shading, factors a professional design adjusts case by case for your home.
Frequently asked questions
Why do peak-sun hours (HSP) matter more than total sunlight hours?
Do I need batteries?
How much roof area per panel?
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The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.