Home – Construction – Homes with solar panels face a new electricity-bill change, and the detail could alter the payoff of rooftop energy
Solar energy has reached the point where the promise feels almost ordinary. Panels are cheaper, batteries are cheaper, and for many families, the idea of cutting the electric bill no longer sounds like a futuristic dream.
Here is the twist, however, for homeowners with solar panels in Brazil, the next big change may not be on the roof. It may be inside the bill itself, where the value of surplus electricity sent back to the grid is becoming more complicated under the country’s distributed generation rules.
The cost collapse behind solar power is real. Latest modeling by the International Renewable Energy Agency (IRENA) shows that between 2010 and 2024, total installed costs fell 87% for solar photovoltaic systems, 55% for onshore wind, and 93% for battery energy storage systems.
That is a huge shift for clean energy. It means the same technologies that once depended heavily on incentives are now competing more directly with traditional power sources, even before counting the everyday things people care about, like less exposure to fuel price spikes or a more predictable monthly bill.
IRENA also projects that the cost of firm solar-plus-battery power could fall roughly 30% by 2030 and around 40% by 2035 under current technology and cost assumptions. In plain English, solar is not just getting cheaper. It is getting better at being available when people actually need electricity.
For a long time, the basic pitch was simple. Put panels on the roof, generate power during the day, send the extra electricity to the grid, and use credits later when the sun goes down.
Brazil’s compensation system still allows consumers with microgeneration and minigeneration to inject surplus power into the local distribution grid and later offset consumption.
Brazil’s National Electric Energy Agency (ANEEL) says those credits can last up to 60 months, and the system includes options such as local self-consumption, remote self-consumption, shared generation, and condominium projects.
The catch is that the grid is not free to run. Wires, poles, transformers, substations, maintenance crews, and control centers all cost money. That is where the charge commonly discussed as “Fio B” comes in.
Brazil’s Law 14,300 created a transition period for distributed generation. ANEEL explains that consumers who requested grid connection by January 6, 2023, keep a full exemption from Distribution System Use Tariff (TUSD) charges until 2045, while later projects move through a gradual transition before a definitive rule takes effect in 2029.
For systems approved after January 7, 2023, the 2026 stage is more noticeable. Canal Solar reports that the portion of “Fio B” no longer compensated rose to 60% this year, meaning only 40% of that component continues to be deducted when credits are applied.
So, what does that mean at home? For the most part, solar still cuts costs, yet a system that sends too much power to the grid and depends heavily on credits may not save as much as expected. The electric bill becomes less about simply producing energy and more about using it at the right time.
The falling cost of batteries changes the conversation. IRENA says battery storage costs fell from $2,634 per kilowatt-hour in 2010 to $197 per kilowatt-hour in 2024, while other industry data cited in the report points to further declines in 2025.
That matters because batteries can help a home use more of its own solar power after sunset. Think air conditioning during that sticky summer heat, dinner-time appliances, phone chargers, computers, and the quiet background load of modern life.
Still, batteries are not magic. They add upfront cost, require the right system design, and may not make sense for every household. As the price keeps dropping, however, they are becoming less of a luxury add-on and more of a practical tool for protecting savings.
Globally, renewables are already winning on cost in many markets. IRENA’s 2024 cost report found that 91% of newly commissioned utility-scale renewable projects delivered electricity more cheaply than fossil fuel alternatives, while 582 gigawatts of renewable capacity were added worldwide that year.
IRENA Director-General Francesco La Camera summed up the trend by saying that the “cost-competitiveness of renewables is today’s reality,” but the same report also warned that tariffs, supply chain pressure, and financing costs could slow the momentum.
That is the lesson for homeowners too. The price of equipment is only one piece of the puzzle. Rules, grid charges, installation quality, consumption habits, and financing terms can all decide whether a rooftop system delivers the savings people expect.
The first thing to check is the system’s approval date. In Brazil, that date can determine whether older compensation protections apply or whether the newer transition rules affect the value of credits.
The second thing is the bill itself. Terms related to injected energy, credit balance, TUSD, and compensation are no longer boring fine print. They can show whether the system is working as planned or whether too much power is being exported at a lower effective value.
At the end of the day, solar still looks stronger than ever, but the smartest users will be the ones who treat their panels, batteries, appliances, and electric bill as one connected system. Cheaper technology helps. Smarter timing may matter just as much.
The study was published on IRENA.
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