How long does a 15kg bag of pellets last? It depends but generally speaking a bag of pellets will last anywhere from 8 to 23 hours of continuous burn. How long a bag of pellets lasts you will depend on your circumstances. This includes what heat output pellet heater you have, how warm you like your house to be, how well insulated your house is and how cold the climate is where you live. All of these factors will greatly impact how many bags of pellets your burn through each winter and thus determine how much it costs to run your pellet heater.
Heater Size and Heat Output
Pellet heaters come in different shapes and sizes, and the the heat output will vary depending on the model and size heater you have. Most pellet heaters, regardless of model or brand, put out a minimum of 3kw and the largest models put out around 13kw of heat. The higher the heat output the more pellets are burnt to create that heat. A small pellet heater that has a maximum heat output of 6kw will burn about half as many pellets as a larger heater that can put out 13kw of heat.
Check the manual of the pellet heater you own or are looking to buy and it should provide a breakdown of how many grams of pellets are burnt per hour for each level of heat output. This is a good starting point as you will be able calculate how many pellets are burnt per hour and that’ll allow you to start calculating how long a 15kg bag of pellets will last.
In the example below from PFTas, you can see that the smaller heaters burn 600 grams an hour on low and 1200 grams per hour on high. This means on low a 15kg bag of pellets would last about 25 hours (15kg / 0.6kg) and on high around 12.5 hours (15kg / 1.2kg). The bigger heaters burn anywhere from 600 grams an hour to 2200 grams an hour. So, on high these larger models would go through a 15kg bag of pellets in 6.8 hours (15kg / 2.2kg). This is probably the quickest and easiest way to work out how long a 15kg bag of pellets will last you.
Pellet Heater Model
You can see from the table above all of those heaters burn a minimum of 600 grams an hour. However, different brands have different burn rates. A burn rate is simply how many pellets are fed into the burn pot, and changing the feed rate on a pellet heater directly impacts the burn rate. I have seen some models with a minimum burn rate of 800 grams and others with a 1kg an hour minimum burn rate. Obviously the higher this minimum burn rate the more heat the pellet heater will put out when running in low. However, please don’t assume that all 12kw pellet heaters, no matter the brand, all have the same feed rate. They don’t.
I have seen Piazzetta pellet heaters with a minimum burn rate of 700 to 800 grams. I have also seen insert pellet heaters with different burn rates to similar kw heat output freestanding units. The burn rate can be adjusted by changing the feed rate but you will find that usually only the retailer will be able to do this. The reason for this is if the feed rate is set incorrectly, it can have a huge impact on how well a pellet heater burns. For this reason I do not recommend you try and adjust the feed rate yourself.
Changing the feed rate too much might mean too many pellets are being fed into the burn pot. If you don’t adjust the exhaust fan to compensate for the extra pellets, you’ll probably find you start getting clinkers or a dirtier burn. You may also find that the fire gets out of control and the burn pot starts filling up with pellets because the feed rate is too high. Like wise, if you change the feed rate so it is too low, it means there may not be enough pellets in the burn pot to keep the fire going. This is why it’s best to let the retailer change the feed rate settings.
How Hot is Hot?
While the manual will detail how many wood pellets are burnt per hour, this is only one factor to consider in how long a bag of pellets will last. This is because how often a heater runs in low or high will depend partly on how warm you like your house to be. Some people are happy with running their heater set at 18 degrees, so there’s a good chance their pellet heater will be in low mode most of the time. For them a 15kg bag of pellets will last much longer than someone who runs their pellet heater on 24 degrees.
Setting the temperature higher will make your heater run in high heating mode longer thus burning more pellets. However, how long your heater runs in high regardless of the temperature you have it set at will depend on the size of the area you are trying to heat. If you live in a small house or are just trying to heat a small area, then it will require fewer pellets to heat than if you were trying to heat a much bigger space or house.
House Insulation
Finally, and possibly the most important thing to find out if you want to know how long does a 15kg bag of pellets last for you is how well insulated your house is. If you have an old, drafty house with no or little insulation and you like to run your heater on 24 degrees, then you will be burning an awful amount of pellets as a lot of the heat will be escaping from the poorly insulated house. These types of houses, what I call igloos, are one of the few reasons you shouldn’t buy a pellet heater.
Even if you do live in a poorly insulated house, spending a little money to fix up the gaps around windows and doors and adding some insulation will go a LONG way to getting more burn time out of a bag of pellets. You may have to spend a few hundred dollars up front to add better insulation but you will find that it will quickly pay off as the house loses less heat, is warmer and you save money by not burning as many pellets.
Summary of How Long a Bag of Pellets Lasts
A 15kg bag of pellets will last anywhere from 8 to 23 hours. However, there’s a lot of factors which come into play and affect how long a bag of pellets lasts. A bag of pellets may last you 10 hours but someone else gets 16 hours from the exact same brand in the same heater. Generally speaking, most people will go through a 15kg bag every 2 days but if you live in a VERY cold area, have an old, poorly insulated house and like to have the temperature around 24 degrees then you will most likely be going through a bag every day and probably quicker due to how much heat your pellet heater is pumping out.
Resources
Quadrafire pellet burn time unformation
