How long does a 15 kg bag of pellets last?

When the cold really bites and the thermometer drops, that 15 kg bag of pellets propped up in the corner suddenly becomes part of the daily routine.

Anyone with a pellet stove or pellet fireplace will recognise the same question: will one bag last through the night, cover a full working day, or disappear in just a few hours? There isn’t a single answer, but you can get to very solid estimates by combining the appliance’s output, your home’s insulation and the way you use it.

Why the same 15 kg bag lasts ages in one home and hardly any time in another

A 15 kg bag of pellets is a common market standard, yet burn time can vary dramatically. In many households it can be anything from under 8 hours to nearly 40 hours. The bag isn’t really the variable; the real difference is the combination of “stove + home + user”.

"A modern stove, properly set up and used in a well-insulated home, can make a 15 kg bag last several days with moderate use."

Newer stoves typically operate at around 85% to 95% efficiency, meaning most of the energy stored in the pellets becomes usable heat indoors. Older units, or appliances that are dirty or poorly adjusted, waste more of that potential and therefore need more fuel to deliver the same level of comfort.

Stove output: the factor that changes burn time the most

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

Pellet stove running at maximum output

When a stove is working close to its limit-often around 8 to 10 kW for domestic models-consumption rises sharply. This is the familiar situation where you set the stove to “max” to warm up a very cold room quickly.

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

At this setting, one bag will rarely cover a full night of severe cold if the appliance stays on full power continuously.

Stove in economy mode or low output

If the stove is run in eco mode-often in the 2 to 3 kW range-the feed rate drops noticeably.

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

"For anyone keeping the stove on low output, a single bag can provide gentle heating for two or three days of limited daily use."

This approach is best suited to well-insulated homes, where indoor temperatures do not swing dramatically throughout the day.

Insulation: the big “invisible villain” behind consumption

Looking only at the stove isn’t enough. The property it’s installed in has a major impact on pellet use. A simple thermal-engineering rule used in many designs is that, on average, 1 kW of output heats around 10 m² under typical conditions.

Situation	Output needed	Effect on the time from a 15 kg bag
Well-insulated 100 m² house	4 to 6 kW most of the time	Moderate duration, balanced use between eco and medium output
Older 100 m² house with no insulation	8 to 10 kW on cold days	Bag used quickly, around 7 to 8 hours at high output
Small, well-insulated flat	Continuous 2 to 3 kW	Bag can get close to 30–40 hours spread across several days

Homes built to modern insulation standards generally demand far less from pellets. By contrast, thin walls, single glazing and gaps around doors create a constant drain of heat.

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

Some of the savings come down to what the user does. Minor routine changes can make a meaningful difference to pellet consumption.

Stove maintenance and cleaning

Smothered embers, built-up ash and partially blocked flues all hinder combustion. The result is straightforward: you burn more pellets to reach the same comfort level.

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

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

Fine-tuning temperature and running times

Using a stove like an electric shower-constantly switching it on and off at maximum-is one of the least efficient habits. It warms the space quickly, but wastes fuel.

Practical settings that help keep costs under control:

• Keep a steady target temperature rather than big peaks
• Use eco mode or a mid-range setting whenever possible
• Programme the appliance to reduce output overnight
• Avoid leaving the stove running at high output when no one is at home

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

Scenario 1: insulated home, moderate use

Picture a well-insulated 90 m² house in a moderately cold area. The stove runs mainly between 2 and 3 kW, with brief climbs to 5 kW early in the evening.

• Average consumption: around 0.6 to 0.8 kg/h, allowing for variation
• Daily use: 8 to 10 hours running
• Result: one 15 kg bag lasts about 2 days in typical use

Scenario 2: older house, harsh winter

In a poorly insulated 100 m² house in a region with severe winter weather, the stove may spend many hours near 8 kW just to offset heat losses.

• Average consumption: close to 2 kg/h on very cold days
• Daily use: 10 to 12 hours
• Result: a 15 kg bag won’t stretch beyond a day of heavy use

How many 15 kg bags you need for a cold season

Once the conversation shifts from “one bag” to “a season”, the scale changes. In many homes where pellets are the main heating source, annual demand is measured in tonnes-not individual bags.

• Well-insulated 100 m² house: roughly 1.5 to 2 tonnes per winter (about 100 to 130 bags of 15 kg)
• Less efficient home or very cold region: consumption can exceed 3 tonnes (more than 200 bags)

"Knowing your home’s average consumption helps you plan stock, negotiate bulk pricing and avoid last-minute price spikes in peak season."

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

Not all pellets are the same. Certified products with low moisture (below 10%) and good compaction burn more consistently and deliver a higher heat output.

Lower-quality pellets often have:

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

In day-to-day terms, that means less heating time per bag and more cleaning effort. Paying slightly more for reliable pellets often pays back in efficiency and comfort.

Terms and details worth knowing before doing the maths

Two ideas come up repeatedly with this topic: efficiency and calorific value. Efficiency is how well the stove converts the pellet’s energy into useful heat inside the home. Calorific value is the amount of energy released when 1 kg of pellets is burned.

So, when a manufacturer states that a stove is 90% efficient, it means that 90% of the available energy warms the room and 10% is lost-much of it carried away in hot gases up the chimney. The higher the efficiency, the more useful heating time you’ll get from each bag.

Quick calculation you can adapt to your own situation

A straightforward way to estimate burn time is to combine three inputs: average output level, hourly consumption and how many hours per day you run the stove. Suppose your stove uses, on average, 1 kg of pellets per hour, and you run it for 8 hours a day under typical conditions.

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

If, over winter, you drop your set temperature by 1 or 2 degrees and lean more on eco mode, overall use tends to fall. Small behavioural changes can translate into dozens fewer bags across a season, without sacrificing basic comfort.