They watch that 15 kg bag pour into the hopper and quietly wonder: is this going to last the evening, the weekend, or almost the whole week? The reply is far from one-size-fits-all, and depends a lot less on luck than on how your home and your stove are set up.
The real question: what does a 15 kg bag actually represent?
Pellet bags look standardised and reassuring, but they don’t all translate into the same number of heating hours. A 15 kg bag of good quality pellets typically contains around 70 kWh of energy on paper. Your stove never uses all of that perfectly, though.
For most modern pellet stoves, you can expect roughly 60 to 65 kWh of useful heat from a 15 kg bag.
That figure is the result of two things:
- the energy content of the pellets themselves
- the efficiency of your stove (how much of that energy turns into usable heat)
A recent, well-maintained appliance usually runs at 85–95% efficiency. An older, poorly serviced stove can fall below 80%, sometimes much less if the glass is blackened and the burn pot is clogged.
How power settings change the lifetime of a bag
Duration is mostly a question of how fast you burn the pellets. And that is set by the power level you choose on the control panel.
At full power: quick comfort, quick consumption
On high, many living-room stoves operate around 8–10 kW. That feels great on a freezing evening, but it eats fuel.
At full power, a 15 kg bag typically lasts only 8 to 10 hours of continuous operation.
In practice, that means a single long winter Saturday can empty the hopper if you leave the stove running flat out from breakfast to bedtime.
In eco mode: slower burn, longer evenings
Switch to eco or low power and the situation changes completely. At 2–3 kW, the stove feeds the flame much more slowly.
Typical ranges look like this:
| Operating mode | Stove power | Approx. pellet use | 15 kg bag duration |
|---|---|---|---|
| Low / eco | 2–3 kW | 0.4–0.6 kg per hour | 25–35 hours |
| Medium | 4–6 kW | 0.8–1.2 kg per hour | 12–18 hours |
| High | 8–10 kW | 1.5–2 kg per hour | 7–10 hours |
This explains why some users claim “a bag lasts me two days” while others barely get an evening out of it. They simply are not using the same power range.
The decisive role of your home’s insulation
The stove does not work in isolation. Your walls, windows and roof decide how much heat is needed to keep you comfortable.
A poorly insulated house can double your pellet consumption compared with a well-insulated home of the same size.
A common rule of thumb is: 1 kW of heating power for roughly 10 m² of living space, assuming reasonable insulation. So a 100 m² house often needs 8–10 kW in a cold snap. In a milder region or in a very efficient building, 4–6 kW may be enough for the same area.
Two contrasting real-life style scenarios
- Modern insulated home, eco mode (around 2 kW): the stove may use about 0.5 kg of pellets per hour. A 15 kg bag then lasts close to 30 hours.
- Old, draughty house, high power (around 8 kW): the stove can consume 2 kg per hour. The same bag disappears in a bit under 8 hours.
Between those extremes, many owners move the power up and down during the day, which spreads the bag life somewhere between a long evening and two or three days of gentle heating.
Pellet quality: why the logo on the bag matters
Not all pellets burn the same. Certified pellets (ENplus, DINplus or local equivalents) generally have low moisture content and consistent density.
Dry, certified pellets burn hotter and longer, which means more hours of heat from each 15 kg bag.
Poor quality pellets, often dustier and wetter, create more ash, clog the burn pot, and lower efficiency. Over time they not only shorten bag life, they can also accelerate wear on the stove and its fan.
How many bags for an entire heating season?
This is the budget question that many households are itching to answer before winter begins. Numbers vary a lot, but some ballpark figures can help.
For a 100 m² home used as a main residence:
- Well-insulated house, moderate climate: around 1.5 to 2 tonnes of pellets a year, or roughly 100 to 130 bags of 15 kg.
- Older house or harsher climate: often 3 tonnes or more, meaning over 200 bags across the season.
If the stove is just a back-up or comfort heating, replacing a gas or electric system for a few hours a day, these numbers fall sharply. Some households manage with only 50–70 bags a year in that case.
Simple habits that stretch each 15 kg bag
Maintenance and cleaning
A clean stove burns better. Regularly emptying the ash pan, brushing the burn pot and checking the flue keeps air circulation steady and efficiency high.
A neglected stove can waste enough energy to cost you several extra bags of pellets every winter.
An annual professional service is usually recommended, especially for stoves used as primary heating.
Smart use of settings and programming
Constant full power is rarely needed. Many users get better results by:
- setting a modest, stable temperature instead of chasing very high comfort levels
- using eco mode once the room is warm
- programming the stove to start slightly before peak cold periods and to cut back at night
A room thermostat or a connected controller can help avoid waste. When the room reaches the target temperature, power falls automatically, and the bag lasts longer without you thinking about it.
Key terms that make pellet use easier to understand
Two technical notions come up again and again in pellet discussions:
- Efficiency (or “yield”): the percentage of the fuel’s energy turned into heat for the room. The higher this is, the more hours of comfort you get from the same bag.
- Power (kW): how fast your stove can deliver heat. High power warms faster but empties the hopper more quickly.
Once you know roughly how many kilos per hour your usual setting uses, you can mentally convert any new bag into hours of heat. That makes storage planning and budget tracking much simpler.
Practical simulations to guide your purchases
Imagine a family in a 90 m² semi-detached house, decently insulated, in a fairly cold region. They run the stove 8 hours a day on medium power, burning about 1 kg per hour. One 15 kg bag then covers nearly two days. Over a four-month peak season, that’s about 60 bags.
Swap the setting to mostly high power, with 1.7 kg per hour, and the maths changes. The same family now needs a new bag almost every day. The season jumps to close to 120 bags, without any change in house size or outside temperature.
A small change in power setting or insulation can save dozens of 15 kg bags over a single winter.
For anyone worried about energy bills, that difference is far from theoretical. It strongly affects how often you haul bags from the garage and how much cash leaves your bank account during the heating season.
