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Residential decision tool · shared generation

Energy subscription — the honest math

Data: July 24, 2026 · Law 14,300/2022 and ANEEL tariffs

You still pay two bills. See how much of the advertised percentage remains after the components that receive no discount.

Offer calculator

How much of the discount reaches the full bill?

Use the percentage and discount base written in the offer. The calculation separates the company invoice from the residual utility bill.

Which base does the contract use for the discount?

Before signing

Four points that change the savings

These are not automatic signs of fraud. They are terms that must be clear because they change the result or make it harder to leave.

  • “Up to X%” or a fixed percentage?

    Look for the formula, not only the headline. “Up to” allows a lower result; even a fixed percentage must state which base it applies to.

  • Credits allocated or actually consumed?

    If billing uses every allocated credit, you may pay for energy carried forward to another month. Prefer billing tied to credits actually compensated on your bill.

  • Exit, notice period and penalty

    Record the minimum term, lock-in, penalty and whether cancellation requires 90 to 180 days’ notice. That range is a contract practice to check, not one statutory SCEE deadline.

  • Who absorbs the rising Fio B charge?

    A rebalancing clause may reduce the discount, change the credit price or pass through new tariff components. Check whether the formula and limit are written down.

Compare with the right alternative

Social Tariff →If you qualify, assess the regulated benefit first.Rooftop solar →If you have a suitable roof and can install, compare on-site generation.Bill auditor →Reconstruct the bill and bring actual figures into this offer.

Sources and limits

  • Law 14,300/2022 — establishes SCEE (Sistema de Compensação de Energia Elétrica, the Electricity Compensation System) and, in art. 27, the Fio B transition: 60% in 2026, 75% in 2027 and 90% in 2028.
  • ANEEL distributed-generation guidance — describes shared generation and confirms minimum billing of 30, 50 or 100 kWh for group B.
  • ANEEL approved tariffs open data — source of current TE and TUSD rates, excluding taxes, used in the calculation.
  • Consumer Protection Code — requires clear information and makes offers binding; the checklist does not replace reading the contract or legal advice.

The comparison excludes taxes: TE, TUSD, Fio B and the tariff flag use the same net basis in both scenarios. Equal tax gross-up would change the displayed reais, not the comparison. Entered COSIP is included in full on both sides.

Without the offer’s unit Fio B value, we estimate it at 35% of TUSD and flag the assumption. Current tariff flags and rates stay constant in the projection to isolate the statutory ramp; after 2028, we assume 90%.

MWatt does not compare companies, recommend suppliers or receive leads. The calculator helps you check an offer you have already received.