Winter is coming, and every year the same question comes up: gas, electricity, or firewood? Recently, a fourth option has been gaining ground in Portuguese homes: biomass and pellets for heating, whether in wood-burning stoves or automatic pellet boilers. But is it really worth switching? Let’s look at the actual numbers, without any empty promises.
- 🔥 Biomass includes firewood, pellets, and briquettes, each with different costs and levels of convenience.
- 💶 A 15-kg bag of pellets currently costs around €5, but the price has fluctuated significantly in recent years.
- ⚙️ An automatic pellet boiler has an efficiency of over 90%, far higher than that of an open fireplace.
- 🏠 It’s more cost-effective in homes with good insulation and central heating than for occasional use in a single room.
- 🛠️ We’ve included a real-life installation example with specific figures further down in the article.
What Counts as Biomass and Pellets for Home Heating
Biomass is any fuel of organic origin: firewood, pellets (compressed sawdust), or briquettes. In practice, for a home in Portugal, this usually comes down to three options:
- Open fireplace: the most traditional, but also the least efficient. Much of the heat escapes through the chimney.
- Wood-burning heat recovery stove: encloses the fireplace within a metal box with glass, often connected to a water circuit (coil) that heats radiators or a hot water tank.
- Automatic pellet boiler: It feeds itself from a silo, starts and shuts off according to a programmed schedule, and connects to the home’s central heating system just as a diesel boiler would.
These are very different solutions in terms of day-to-day convenience, but they all share the same fundamental advantage: the fuel is domestically sourced (or European), cheaper per kWh than electricity in many scenarios, and not dependent on oil prices.
How much does it really cost to heat a home with pellets?
A 15-kg bag of pellets currently costs between €4 and €6 at major retailers, depending on the brand—about €0.30 to €0.40 per kilogram. When purchased in bulk (pallets of 60 bags), the price per kilogram drops slightly. This is not a fixed price: the pellet market has fluctuated with European demand, so it’s always worth checking the price before making a decision.
For an automatic boiler, consumption depends mainly on three factors:
- Home insulation (a poorly insulated home uses much more fuel to maintain the same temperature);
- Equipment efficiency (modern, certified boilers easily exceed 90% efficiency, compared to 60–70% for an old wood-burning stove);
- The area and number of rooms that are actually being heated.
A wood-burning stove works differently: if you have access to your own firewood or can get it at a low price, the cost per kWh can be even lower than that of pellets, but it requires more manual labor (stoking the fire, cleaning out ashes more frequently).
Biomass vs. Heat Pump: Which to Choose
The most common question we hear at LEFE isn’t “firewood or pellets,” but rather “biomass or heat pump.” There’s no single answer: it depends on your usage profile.
| Criteria | Biomass boiler/stove | Heat pump |
|---|---|---|
| Efficiency | Efficiency up to ~90% (fuel combustion) | 3 to 5 kWh of heat per 1 kWh of electricity |
| Fuel cost | Pellets or firewood, more stable in the long term | Electricity, subject to the contracted rate |
| Irregular use (weekends, evenings) | Very flexible; starts and stops without losing efficiency | Loses efficiency when used only occasionally |
| Maintenance | Ash and chimney cleaning, annual inspection | Refrigerant and filter inspection |
| Initial investment | Medium to high (silo, flue piping) | Variable, generally lower for split-system models |
In practice, those who heat their entire home at set times and have access to a low-cost electricity rate tend to prefer heat pumps. Those who heat more irregularly, live in a cold part of the country, or already have access to firewood or pellets at a good price tend to prefer biomass. And there are even those who combine the two: a heat pump for everyday use and a wood-burning stove for the coldest days of the year.
Real-world example: a larger-scale pellet boiler, with actual figures
In 2024, LEFE installed in a social housing building in the Famalicão area (name and address omitted for confidentiality) two Solius AutoPellets boilers, each with a capacity of 60 kW, featuring automatic burner and boiler body cleaning, automatic ash removal, and a 500-liter silo per unit. This is an institutional-scale installation, much larger than a residential one, but the figures are real and help illustrate the order of magnitude:
- Nominal efficiency: 90.8%, according to the equipment’s technical specifications.
- Total system investment (2 boilers + 1,000-liter buffer tank + 2,500-liter domestic hot water tank + accessories).
- Redundancy: We opted for two smaller boilers instead of a single larger one to ensure heating even if one of them requires maintenance.
In a single-family home, the required power is much lower (typically between 15 and 30 kW, depending on the area and insulation), so the investment is proportionally lower. Even so, this example clearly illustrates what to expect from a certified automatic boiler: high efficiency, operation without daily intervention, and an investment that pays for itself over several winters of use.
How to Know If It’s Worth It for Your Home
- ☑️ Does the house have space for a pellet silo or to store dry firewood?
- ☑️ Is there (or is it feasible to install) a suitable flue?
- ☑️ Is the heating system central (radiators, underfloor heating) or limited to a single room?
- ☑️ Do you have access to firewood at a good price, or will you always have to rely on buying pellets?
- ☑️ Are you willing to perform regular maintenance (cleaning out ashes, annual chimney inspection)?
If you answered “yes” to most of these questions, biomass is most likely an option worth seriously considering. If you answered “no” to most of them, it might be better to first look into a heat pump or improving your home’s insulation.
Maintenance: What Changes in Your Daily Routine
A common question is how much extra work biomass involves compared to a gas boiler or a heat pump. The honest answer is: some, but it’s manageable.
- Ash removal: In an automatic boiler with automatic ash removal, this step is practically negligible; in a manual wood-burning stove, you’ll need to empty the ash drawer regularly.
- Chimney and flue: These should be inspected and cleaned at least once a year to prevent soot buildup.
- Supply: Pellet silos can last for weeks without being refilled; firewood requires a dry, organized storage space.
- Annual equipment inspection: Just like a gas boiler, the burner and mechanical components benefit from an annual technical inspection, especially for equipment that sees heavy use.
None of this is a deal-breaker, but it’s fair to say that those seeking the least possible maintenance tend to prefer a heat pump. Those who don’t mind this routine—in exchange for a more predictable fuel bill—are usually satisfied with biomass.
Conclusion
There is no one-size-fits-all answer to the question “Is it worth heating your home with biomass?”—it depends on the type of home, access to fuel, and usage patterns. What is certain is that, when properly sized and installed, a pellet boiler or a wood-burning stove remains one of the most efficient ways to heat a Portuguese home in the winter, using a fuel that doesn’t depend on the price of oil or natural gas.
Want to know if biomass is a good fit for your home? The LEFE team will assess your situation—including the required heat output, type of equipment, and available space—and propose a customized solution, with no obligation.
