How long does a 15 kg bag of pellets last?

As the cold sets in and the temperature drops, the 15 kg bag of pellets sitting in the corner becomes an increasingly important part of everyday life.

Anyone with a pellet stove or fireplace will know the question well: will that bag last all night, throughout a working day, or only for a few hours? There is no single answer, but realistic estimates can be made by considering the appliance output, the home’s insulation and the way it is used.

Why the same 15 kg bag lasts much longer in some homes

A 15 kg bag of pellets is a standard market size, yet its burn time can vary considerably. In many situations, it may last from under 8 hours to almost 40 hours. The difference lies less in the bag itself and more in the combined effect of the “stove + home + user”.

A modern, properly adjusted stove in a well-insulated home can make a 15 kg bag last for several days of moderate use.

Recent stoves typically achieve efficiencies of between 85% and 95%. In other words, almost all the energy contained in the pellets becomes usable heat. Older, dirty or poorly adjusted models waste more of that potential, requiring extra fuel to provide the same feeling of warmth.

Pellet stove output: the factor that most affects burn time

The output, measured in kW, is the starting point for understanding how long a 15 kg bag will last on average.

Pellet stove at maximum output

When the appliance is running close to its limit, usually around 8 to 10 kW for domestic models, consumption rises sharply. This is the familiar situation where someone turns the stove up “to maximum” to heat a freezing room quickly.

• High output (8 to 10 kW)
• Approximate consumption: 1.5 to 2 kg of pellets per hour
• Duration of a 15 kg bag: roughly 7 to 10 hours

At this setting, one bag is unlikely to last through a particularly cold night if the appliance runs continuously at maximum power.

Stove in eco mode or at low output

When a stove operates in eco mode, generally between 2 and 3 kW, the pellet feed rate falls substantially.

• Low output (2 to 3 kW)
• Approximate consumption: 0.4 to 0.6 kg of pellets per hour
• Duration of a 15 kg bag: between 25 and 40 hours

For those who keep their stove at low output, one bag can provide gentle heating for two or three days of limited daily use.

This setting is most suitable for well-insulated homes, where temperatures do not fluctuate significantly during the day.

Insulation: the major invisible cause of pellet consumption

It is not enough to consider the stove alone. The home where it is installed has a major impact on the calculation. A straightforward thermal-engineering rule used in many projects is that, on average, 1 kW of output heats around 10 m² in typical conditions.

Situation	Required output	Effect on the life of a 15 kg bag
Well-insulated 100 m² home	4 to 6 kW for most of the time	Moderate duration, with balanced use between eco and medium output
Older 100 m² home without insulation	8 to 10 kW on cold days	Bag used quickly, lasting 7 to 8 hours at high output
Small, insulated flat	Continuous 2 to 3 kW	Bag may last close to 30–40 hours, spread across several days

Homes built to modern thermal-insulation standards generally demand far less from the pellets. Thin walls, single-glazed windows and draughts around doors, by contrast, create a constant escape route for heat.

How to make every 15 kg bag last longer without feeling cold

Part of the equation is under the user’s control. Small changes to daily habits can make a genuine difference to pellet consumption.

Pellet stove maintenance and cleaning

Smothered embers, accumulated ash and partially blocked flues interfere with combustion. The result is more pellets burned for the same level of thermal comfort.

• Clean the burn pot regularly
• Remove ash from the internal compartments
• Arrange periodic servicing of the stove and chimney

A clean, properly adjusted stove burns more efficiently, produces more heat per kilogram of pellets and needs fewer bag refills.

Fine-tuning temperature and operating times

Using a stove like an electric shower, by switching it “on and off at maximum”, is the least efficient approach. It warms the space quickly, but uses fuel unnecessarily.

Useful settings for keeping costs under control include:

• Maintaining a steady target temperature without major peaks
• Using eco mode or medium output whenever possible
• Programming the appliance to reduce output overnight
• Avoiding running the stove at high output when nobody is at home

Real-world scenarios: how long does a bag actually last?

Scenario 1: insulated home, moderate use

Consider a well-insulated 90 m² home in an area with moderately cold weather. The stove operates mostly between 2 and 3 kW, with 5 kW peaks at the beginning of the evening.

• Average consumption: around 0.6 to 0.8 kg/h, allowing for variations
• Daily use: switched on for 8 to 10 hours
• Result: one 15 kg bag lasts around 2 days of typical use

Scenario 2: old house, severe winter

In a poorly insulated 100 m² home in an area with harsh winters, the stove runs close to 8 kW for many hours as it tries to offset heat losses.

• Average consumption: close to 2 kg/h on very cold days
• Daily use: 10 to 12 hours
• Result: one 15 kg bag does not last beyond a day of intensive use

How many 15 kg bags are needed for a cold season?

Once the discussion moves from “one bag” to “a whole season”, the scale of the calculation changes. In many homes heated mainly by pellets, annual demand is measured in tonnes rather than individual bags.

• Well-insulated 100 m² home: between 1.5 and 2 tonnes per winter (around 100 to 130 15 kg bags)
• Less efficient home or very cold area: consumption can exceed 3 tonnes (more than 200 bags)

Knowing your home’s average consumption helps you plan your stock, negotiate bulk prices and avoid last-minute price rises during peak season.

Pellet quality: a detail that changes the burn-time clock

Not every pellet is the same. Certified products with low moisture content, below 10%, and good compaction burn more consistently and offer greater calorific value.

Poor-quality pellets tend to have:

• More dust and residue in the bag
• Uneven combustion with unstable flames
• Excessive ash and deposits

In practice, this means less heating time from each bag and more cleaning work. Paying slightly more for reliable pellets generally pays off in day-to-day use, both in efficiency and comfort.

Terms and details worth understanding before doing the calculation

Two concepts often arise in this subject: efficiency and calorific value. Efficiency refers to the stove’s ability to convert pellet energy into usable heat inside the home. Calorific value, meanwhile, is the amount of energy that 1 kg of pellets can release when burned.

When a manufacturer states that an appliance has 90% efficiency, it means that, of all the energy available in the fuel, 90% effectively warms the space and 10% is lost, largely through the hot gases in the chimney. The greater the efficiency, the longer the useful heating time from each bag.

A quick calculation to adapt to your own situation

A simple way to estimate burn time is to combine three figures: the average output used, hourly consumption and the number of hours of use each day. Suppose your stove uses an average of 1 kg of pellets per hour and you run it for 8 hours a day under normal conditions.

• Daily consumption: 8 kg
• 15 kg bag: lasts close to 1 and a half days
• 4-month season (120 days): close to 960 kg, or 64 bags

If you lower the target temperature by 1 or 2 degrees over the winter and make greater use of eco mode, consumption is likely to fall. Small behavioural changes can mean dozens fewer bags over a season, without having to sacrifice basic comfort.