Brazil Solar Panel Calculator: System Size, Cost and Payback
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This calculator turns a Brazilian electricity bill into a solar system: array size in kWp, number of panels, installed cost, monthly savings and payback in years. It applies the 2026 rules of Law 14,300 — under which 60% of the Fio B grid component is charged on offset energy — and defaults to the September 2026 national residential rate of R$0.95/kWh.
How grid-tied solar works in Brazil
Almost every Brazilian residential installation is grid-tied and battery-free. Panels generate during the day, an inverter converts to AC, the house uses what it needs, and the surplus flows to the grid as kWh credits recorded by a bidirectional meter. At night the house draws from the grid and burns those credits. Credits last 60 months and can be applied to other accounts held by the same owner within the same utility area.
Two consequences matter. First, your bill never reaches zero: the availability charge — a minimum of 30 kWh on single-phase, 50 kWh on two-phase and 100 kWh on three-phase connections — is billed every month regardless of generation. This calculator subtracts that minimum before sizing the array, because paying for panels to generate energy you will be charged for anyway makes no sense. Second, a grid-tied system shuts down during a blackout for the safety of line workers; riding through outages requires a hybrid system with batteries, which is a different and costlier calculation.
Law 14,300 and the Fio B charge
Until 2022 offsetting was one-for-one across every tariff component. Law 14,300/2022, the distributed generation legal framework, phases in a charge for Fio B — the TUSD component that pays for the distribution wires and transformers you still use to push and pull energy. The share billed to the consumer started at 15% in 2023 and rises 15 points a year: 30% in 2024, 45% in 2025, 60% in 2026, 75% in 2027, 90% in 2028 and 100% from 2029.
In numbers, a customer in CPFL Paulista territory injecting 1,000 kWh forgoes R$123.90 in credits in 2026 — R$0.1239/kWh, which is 60% of a full Fio B of roughly R$0.2065/kWh. Grossed up for ICMS and PIS/COFINS that is about R$0.15 per kWh, or roughly 15% of a R$0.95 tariff, so this calculator treats 85% of each offset kWh as real savings. Systems whose grid connection was filed on or before January 6, 2023 keep full exemption until 2045.
Sizing, cost and payback
One installed kWp generates about 120 kWh per month on the Brazilian national average, ranging from 105 kWh in Curitiba to 135 kWh in Petrolina depending on peak sun hours. Divide your offsettable consumption by that figure to get the array size, then divide by the panel rating — 600 Wp is the 2026 residential standard, with the market spanning 550 to 620 Wp.
Installed cost ran between R$3,500 and R$5,500 per kWp in 2026, all in: panels, inverter, racking, cabling, engineering, permitting and labor. Larger systems cost less per kWp, around R$5,000 at 3 kWp against R$3,700 at 8 kWp. Panels carry a 25-year performance warranty and degrade about 0.5% a year; the inverter is normally replaced around year 12 at roughly 20% of system value.
A useful and counter-intuitive result: payback does not depend on the size of your bill, because investment and savings scale together. It depends on the price you pay per kWp and on your tariff. At the R$4,500/kWp and R$0.95/kWh defaults, payback is 3.87 years; at R$3,500/kWp with a R$1.10 tariff it drops to 2.60 years, and at R$5,500/kWp with a R$0.80 tariff it stretches to 5.62 years.
Getting a quote that holds up
Collect at least three quotes and insist that each one states the array size in kWp, the estimated monthly generation in kWh, the irradiation figure used (from the free CRESESB/SunData database), the make and model of panels and inverter with their warranties, and whether the price covers the electrical design, the engineer sign-off, utility approval and any upgrade to the service entrance — the last of which is the most common cost surprise.
Treat three things as red flags: demanding full payment before installation, promising a zero electricity bill (impossible because of the availability charge), and a savings simulation that ignores the Fio B phase-in. Solar financing is widely available at 36 to 84 months; if the installment is smaller than the monthly savings shown above, the system pays for itself from month one. Compare total effective cost, not headline rates.
Frequently asked questions
How many solar panels do I need?
Subtract the availability minimum (30, 50 or 100 kWh) from your monthly consumption, divide the remainder by 120 kWh — the average monthly output of 1 kWp in Brazil — and divide the result by your panel rating. With 600 Wp panels, a R$400 bill on a single-phase connection needs 3.26 kWp, or 6 panels; a R$700 bill needs 5.89 kWp, or 10 panels.
Is solar still worth it in Brazil in 2026?
Yes, with a thinner margin than in 2022. With 60% of Fio B charged, real bill savings land between 80% and 87% rather than near 100%, and typical payback runs 3.5 to 8 years against a 25-year module life. Because the charge climbs 15 points a year until 2029, installing earlier locks in more years of favourable offsetting.
Will my electricity bill go to zero?
No. The availability charge (30, 50 or 100 kWh depending on your connection), public lighting fees and the Fio B share on offset energy remain. A R$400 single-phase bill typically falls to around R$84 a month. Any installer promising a zero bill is either out of date or misleading you.
What does a residential solar system cost in Brazil?
Between R$3,500 and R$5,500 per installed kWp in 2026. In practice a 3 kWp system runs R$13,000–17,000 and an 8 kWp system R$26,000–33,000. The North and Northeast pay up to 20% more because of freight and fewer competing installers, though stronger irradiation partly offsets that.
Sources
Reference estimate, not a quote. Results assume 120 kWh per kWp per month (the national average; real output runs from 105 kWh in the South to 135 kWh in the Northeast and depends on roof tilt, orientation and shading), 600 Wp panels, R$4,500 per installed kWp, and a 15% haircut on offset energy to represent the 60% Fio B charge in force in 2026 under Law 14,300 — a share that rises 15 points a year to 100% in 2029. It excludes service-entrance upgrades, inverter replacement around year 12, annual module degradation and future tariff changes. Obtain at least three quotes from established companies and require the sizing calculation for your own city before committing.
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Also available in Portuguese: Calculadora de energia solar: quantas placas e em quanto tempo se paga