Portugal warms the cold days driven by the power of renewable energies

The cold tightened, and the country responded with clean energy: on the coldest days, the electricity that warmed homes primarily came from water and wind. This guide shows you how to take advantage of this collective force to heat your home efficiently, comfortably, and sustainably.

Portugal warms cold days driven by the power of renewable energy: data, peaks, and what this means for your home

During intense cold weeks, national electricity consumption surpassed old records, and yet, the system responded with safety and renewables. There was a historic record from 2021 that fell not once, but six times in a single month, signaling that home heating has come to depend more on electricity and less on fossil fuels. This was only possible with hydropower and wind producing on a large scale during a rainy and windy winter.

The numbers help to understand the magnitude. On days 6 (186.2 GWh), 7 (188.1 GWh), 8 (192.4 GWh), 20 (193.9 GWh), 22 (195.5 GWh), and 23 (198.1 GWh), according to data released by REN, the demand reached levels that would have required, in other times, the activation of gas plants for long hours. This time, the bulk came from water in the reservoirs and wind in the mountains, with solar helping to ease the daytime profile. For you, this translates to a more stable energy bill and a network less vulnerable to external shocks.

This behavior did not arise from nowhere. Portugal had closed recent years with very high renewable integrations: in 2024, months like April managed to cover about 95% of electrical needs with clean sources, and during other rainy periods, there were several consecutive days with fully renewable production. In 2026, what changed was the combination of greater installed capacity (onshore wind and hydropower reinforcement), better grid management, and consumers who shifted some heating to more efficient electric solutions, like heat pumps.

For your home, the message is clear: when it rains and blows, electricity tends to be cleaner and often cheaper at the right times. If your heating is efficient electric and the house has a good thermal envelope, it is possible to maintain comfort with controlled costs. At the same time, heating with electricity on windy and rainy days reduces emissions and improves local air quality, avoiding inefficient combustions or old equipment.

Peaks, flexibility, and savings opportunities

Peak hours still exist, especially in the late afternoon and early evening. But renewable availability also increases during these windows, especially with wind. Grids are already exploring demand-side flexibility, encouraging consumption shifts to favorable periods. With a simple adjustment of schedules and the use of your home’s thermal mass, you can preheat before the peak and leave the temperature stabilized effortlessly. If you have radiant floors or low-temperature heaters, this effect is even more effective.

To illustrate better, see a summary of record days and the source that contributed the most. This is not an official report, but a useful snapshot to understand trends and decide when to heat more intensely.

The key point is clear: the grid can already supply winter peaks with renewables. It is up to each home to adjust to reap the benefits in comfort and cost.

How to heat your home with renewable energies without complicating things: priorities, choices, and tricks that work

The best strategy for heating with clean energy starts where heat is lost: in the walls, windows, and roofs. Next, you choose the system that converts renewable electricity into heat with the highest efficiency. Finally, organize use with schedules and simple automation. This order of priorities avoids investments that don’t pay off and accelerates results.

Priority 1: thermal envelope. Doors that don’t seal, old windows, leaky shutter boxes, and ceilings without insulation drag any system to excessive consumption. A typical intervention in a T2 might include sealing joints, adjusting thermal curtains, sealing shutter boxes, and, when possible, replacing with low-emission glass. In houses, the gain in comfort is even greater when reinforcing attic insulation with natural materials like cork or wood fiber.

Priority 2: heat pump. For heating, a good energy-class split air-to-air unit can show COP 3–4 in mild conditions; on very cold days, this value decreases but stays above 2 in most cases, which is already significantly better than electric resistance (COP ≈ 1). Those with radiant floors and air-to-water pumps can operate at low supply temperatures (30–35 °C) and achieve superior efficiency, especially if they preheat before peak times and leverage slab inertia.

Priority 3: controls and habits. Programmable thermostats, outdoor probes on air-water pumps, and well-defined zones in the home allow heating where needed, at the right time. Adopting simple habits — like closing shutters at dusk, using rugs on cold floors, and concentrating presence in fewer rooms on the coldest nights — can save as much as changing equipment.

Practical step-by-step that works

• 🧱 Seal first: sealing tape on frames, foam in shutter boxes, and brushes on doors minimize infiltration.
• 🪟 Efficient windows: if you can’t replace them yet, apply low-emission films and properly sized “heavy” curtains.
• ⚙️ Choose the right heat pump: size it for 85–95% of the load; it avoids short cycles and improves comfort.
• 🕒 Schedule times: preheat 1–2 hours before the peak and maintain a constant temperature.
• 🌞 Solar gains: open shutters to winter sun and close them as soon as it gets dark.
• 💧 Humidity: maintain 40–60%; dehumidifying improves thermal sensation and reduces condensation risks.

A realistic example: in a 78 m² apartment in Braga, replacing two oil heaters with a 3.5 kW air-to-air heat pump, combined with sealing windows and thermal curtains, reduced monthly consumption by about 35–45% during cold spells while maintaining 20–21 °C. The key was controlling schedules and closing shutters at night, preserving the accumulated heat at the end of the afternoon.

Avoid common traps

Avoid using electric resistance as the main solution — it is only valid as a backup. Do not program overly high temperatures (23–24 °C) that exponentially increase consumption; 20–21 °C is the “sweet spot” for most homes. If the property is very air-permeable, sizing a larger heat pump won’t solve the issue; first, seal the leaks. And finally, remember: comfort comes from a whole — envelope + system + use — not from an isolated piece of equipment.

With this method, heating aligns with the strength of renewables without complications, and your bill goes down.

Bioclimatic architecture and natural materials: retaining heat with less energy on cold days

When the house helps, everything becomes easier. Good bioclimatic architecture uses the climate to its advantage, reduces losses, and improves comfort without constantly relying on the active system. Even in existing buildings, there is much to be done: orienting uses, leveraging winter sun, creating wind barriers, and using natural materials with good thermal performance.

Start with passive solar gains. In winter, south-facing facades can receive generous sunlight; letting light in in a controlled manner warms surfaces and air, raising the base temperature. Low-emission glass with a solar factor adapted to orientation allows heat to enter and retains some of it at night. Deciduous plants outside act as seasonal “brises”: they let in sun in winter and provide shade in summer.

Next, focus on thermal inertia. Walls with mass — such as rammed earth, solid brick, or concrete — absorb part of the heat and release it slowly. Combined with low-temperature radiant floors or solar gains during the day, this “reservoir” smooths fluctuations and reduces frequent starts of the heat pump. For those living in apartments, thick carpets and full bookshelves also offer small heat reserves and enhance comfort sensation.

Natural materials add performance and interior environmental quality. Expanded cork, abundant in Portugal, insulates, regulates humidity, and has a low carbon footprint. Wood fiber and hemp-lime combine insulation and vapor diffusion, protecting the house from hidden condensations. In rehabilitations, “breathable” solutions prevent issues in old walls and maintain healthy finishes.

Insulation, airtightness, and ventilation: the trio that makes a difference

It’s easy to talk about insulation and forget about air tightness. A house that is well insulated but has open gaps remains cold and expensive. Specific adhesive tapes for frames, membranes in false ceilings, and attention to plumbing passes eliminate “invisible drafts.” At the same time, controlled ventilation (ideally with heat recovery in more ambitious projects) renews the air and retains energy, solving the comfort + health equation.

To guide choices, see a simplified comparison with common materials in ecological rehabilitation. The values are typical and help to understand the “character” of each solution.

Case study: in an 80s house in Viseu, applying 80 mm of cork to the ceiling, sealing window frames, and thermal curtains increased the average nighttime temperature by 2–3 °C without any changes to the heating system. When, months later, an air-to-water heat pump arrived, the house began to maintain 20–21 °C with stability and fewer start cycles.

In summary, bioclimatic design adds up to “small gains” that together create robust comfort. The less energy the house needs, the more it “tows” the wind and water — and you can feel it, in your body and in your budget.

From the grid to the outlet: tariffs, self-consumption, and smart management during demand peaks

With the grid supplying more clean energy, the difference lies in how you use it. Bi-hourly and tri-hourly tariffs, scheduling management, and small daily adjustments amplify the effect of renewables and reduce your bill. Think of your heating as a “thermal battery”: it charges during the right periods, releasing comfort when needed.

First, know your tariff. If you already have bi-hourly, schedule heating during the empty periods and maintain temperature with gentle increments during peaks. In tri-hourly, the full periods often concentrate in the late afternoon; preheat 60–120 minutes ahead. Thermostats with “optimized start” kick in earlier when it’s very cold and avoid violent peaks at expensive times.

Next, consider self-consumption. Even in winter, photovoltaic panels generate a good part of the day. If you have an air-to-water heat pump, direct domestic hot water (DHW) production to sunny hours and slightly reduce the setpoint of the house after sunset to avoid the system compensating fully. A small buffer tank improves stability and better utilizes production windows.

Finally, explore energy managers and retailer apps. Seeing real-time consumption graphs changes habits: it’s immediate to perceive the impact of turning on an old radiator versus using the heat pump in Eco mode. In buildings with multiple apartments, a coordinated heating strategy outside of peak times can reduce the contracted power for each unit, lowering fixed costs.

Simple routine for cold nights

On windy and rainy afternoons, renewable availability tends to be high. Take advantage to preheat, close shutters at dusk, and stabilize the house between 20–21 °C. If you have radiant floors, anticipate even more. And if you wake up to a cold house, schedule the “start” an hour before your daily routine during the cheaper energy periods.

The result is a comfortable home that follows the flow of renewables: heating when there is abundance and moderating when the system is under more pressure. This is how each consumer becomes an active part of the transition.

Preparing for the next winters: checklist and action plan that respects your budget

Last winter showed that clean energy is ready. The missing part is ensuring that your home is as well. The best way is a step-by-step plan, starting with what costs little and yields much, and advancing to structural investments when it makes sense. It’s not necessary to do everything at once; the secret is the right order.

Start with a “light diagnosis.” Walk through the house on a cold night with a candle or incense and observe where the flame flickers — it’s the simplest way to detect infiltrations. Notice the windows that fog up: there, the surface is cold and humidity is higher. Take thermal photos with your phone (there are apps and small accessories that help) to visualize thermal bridges. With this information, move on to quick actions.

• 🪟 Today: seal frames, close shutters at night, adjust curtains.
• 🔧 This month: review heat pump parameters, install a programmable thermostat, create two or three “usage zones” at night.
• 🧱 In the next 3–6 months: insulate attic ceiling with cork/wood fiber, improve shutter boxes, evaluate replacing more exposed windows.
• ⚙️ When possible: install a heat pump sized for space, consider low-temperature radiant floors in more ambitious renovations.

For families with limited budgets, the rule is to prioritize what reduces losses. A roll of sealing tape and a well-mounted thermal curtain kit can lower the necessary power on cold nights, allowing the heat pump to operate with less effort. If you live in a building with an active condominium, propose joint interventions on roofs and façades: the cost per unit drops, and the impact adds up.

It’s worth documenting everything: photos, temperatures, consumption. Over a month of cold, it’s common to see reductions of 20–30% in consumption for the same comfort temperature just by adjusting sealing, schedules, and set points. When the time comes to invest in a new window or heat pump, this data helps to choose the right solution, neither the most expensive nor the weakest.

A simple action to start right away: choose two fixed preheating times for the next cold nights (e.g., 06:30–08:00 and 17:30–20:00), close shutters, and check if the temperature remains stable in the following hours. If it works, consolidate; if it oscillates, adjust sealing and curtains first. Winter rewards those who prepare the house like a well-buttoned coat: the wind blows outside, comfort stays inside.

Source: jornaleconomico.sapo.pt