Is rooftop solar worth it at your home?
Full result on screen — no phone number or email required.
Example: São Paulo/SP
Two-phase home with 400 kWh/month on CPFL Paulista, irradiance of 4.7 kWh/m²·day (INPE/LABREN, 2017) and effective tariff of R$ 0,91/kWh (ANEEL · as of Jan/2025) (Fio B R$ 0,25/kWh). System costs: Greener 2025. Result already in the HTML — adjust the form above with your bill.
São Paulo/SP · 400 kWh/month · CPFL Paulista · R$ 0,91/kWh (ANEEL · as of Jan/2025) · Fio B R$ 0,25/kWh
Investment pays back in
2 years 10 months
Savings of R$ 283/month already in year one · R$ 161.155 over 25 years (net)
System
3.4 kWp
Panels
6 × 570 Wp
Roof area
15.6 m²
Investment
R$ 9.747
Residential battery: we don't model that yet — hub BESS is for auction-scale (≥30 MW).
Lei 14.300 is already in the math ✓
Energy you inject into the grid pays a rising share of “Fio B” (60% in 2026, reaching 90% in 2028). Our simulation deducts that year by year — in your case, R$ 420 in year one. See how we calculate (in Portuguese)
With financing, does the installment fit where the bill was?
On a typical 96-month plan (1.35%/mo), the installment is R$ 181,75/month/month against savings of R$ 283,48/month in year 1 — positive cash flow of R$ 101,73/month from the start. Banks like Santander and BV finance from 96 to 144 months.
🌱 Environmental impact
~7.5 tonnes of CO₂ avoided over 25 years — equivalent to planting ~46.9 trees.
See year-by-year detail (full transparency)
| Year | Generation (kWh) | Fio B | Fio B cost | Net savings | Cumulative |
|---|---|---|---|---|---|
| 2026 | 4,548 | 60% | R$ 420 | R$ 3.402 | -R$ 6.345 |
| 2027 | 4,525.3 | 75% | R$ 558 | R$ 3.493 | -R$ 2.852 |
| 2028 | 4,502.7 | 90% | R$ 712 | R$ 3.583 | R$ 731 |
| 2029 | 4,480.2 | 90% | R$ 756 | R$ 3.796 | R$ 4.527 |
| 2030 | 4,457.8 | 90% | R$ 803 | R$ 4.022 | R$ 8.548 |
| 2031 | 4,435.5 | 90% | R$ 854 | R$ 4.261 | R$ 12.809 |
| 2032 | 4,413.3 | 90% | R$ 907 | R$ 4.515 | R$ 17.324 |
| 2033 | 4,391.2 | 90% | R$ 964 | R$ 4.783 | R$ 22.107 |
| 2034 | 4,369.3 | 90% | R$ 1.024 | R$ 5.068 | R$ 27.175 |
| 2035 | 4,347.4 | 90% | R$ 1.088 | R$ 5.370 | R$ 32.545 |
| 2036 | 4,325.7 | 90% | R$ 1.155 | R$ 5.689 | R$ 38.234 |
| 2037 | 4,304.1 | 90% | R$ 1.227 | R$ 6.028 | R$ 42.800 |
| 2038 | 4,282.5 | 90% | R$ 1.304 | R$ 6.387 | R$ 49.187 |
| 2039 | 4,261.1 | 90% | R$ 1.385 | R$ 6.767 | R$ 55.953 |
| 2040 | 4,239.8 | 90% | R$ 1.472 | R$ 7.170 | R$ 63.123 |
| 2041 | 4,218.6 | 90% | R$ 1.563 | R$ 7.596 | R$ 70.719 |
| 2042 | 4,197.5 | 90% | R$ 1.659 | R$ 8.044 | R$ 78.763 |
| 2043 | 4,176.5 | 90% | R$ 1.750 | R$ 8.484 | R$ 87.248 |
| 2044 | 4,155.6 | 90% | R$ 1.846 | R$ 8.948 | R$ 96.196 |
| 2045 | 4,134.9 | 90% | R$ 1.947 | R$ 9.438 | R$ 105.634 |
| 2046 | 4,114.2 | 90% | R$ 2.053 | R$ 9.954 | R$ 115.588 |
| 2047 | 4,093.6 | 90% | R$ 2.166 | R$ 10.498 | R$ 126.086 |
| 2048 | 4,073.2 | 90% | R$ 2.284 | R$ 11.073 | R$ 137.159 |
| 2049 | 4,052.8 | 90% | R$ 2.409 | R$ 11.678 | R$ 148.837 |
| 2050 | 4,032.5 | 90% | R$ 2.541 | R$ 12.317 | R$ 161.155 |
Includes panel degradation (0.5%/year), inverter replacement in year 12, and annual tariff inflation.
What we estimated (and why)
- Effective tariff estimated from CPFL Paulista's approved tariff + average taxes (~30%) — ANEEL · as of Jan/2025.
- The Fio B rule after 2028 is still to be set by ANEEL — we assume it stays at 90% (the most-cited conservative scenario).
- Investment estimated from market bands (Greener, 2025) — get real quotes for the exact figure; typical spread ±15%.
This is an educational estimate, not a commercial offer. Full methodology and sources (in Portuguese) →
| Performance ratio | 78% |
|---|---|
| Self-consumption | 30% of generation |
| Panel degradation | 0.5% per year |
| Tariff inflation | 6% per year |
| Investment (Greener) | 2025 market bands |
| Fio B after 2028 | 90% (conservative scenario) |
Sources and details in Methodology (in Portuguese).