What factors determine the required boiler power for central heating? Why is it not advisable to buy a boiler with a higher nominal power than needed? How does the quality of insulation in the heated space affect the boiler’s power? Why is professional assessment indispensable?
When installing central heating for the first time, it is best to leave the determination of boiler power to a professional who designs the heating system. However, it is quite common to replace an old existing boiler with a new pellet or gas boiler, and in such cases, it is also possible to leave the choice of boiler to a professional.
In fact, every boiler manufacturer, whether for pellet or gas boilers, requires that the boiler be installed by a professional in order for the warranty to be approved. Therefore, consult with the technician you plan to hire for the installation before making a purchase.
Related Articles:
Five Common Misconceptions About Underfloor Heating
Clean Your Radiators and Boost Heating Efficiency by 30%
All About Heating with Pellets
Defining the boiler’s power is of great importance. It is clear that the boiler should not have a lower nominal power than needed, as it will often have to operate at full capacity and under heavy load, and there is a question of whether the house will be warm enough.
On the other hand, purchasing a boiler with a higher nominal power than necessary may seem like a minor mistake, but it’s not quite so. Firstly, buying a more powerful boiler than required means you spent more money than necessary on the device itself.
The second problem is that an overly powerful boiler will often need to operate in an economical mode, which will be especially pronounced during transitional periods when it’s not cold outside. During these times, fuel consumption will also be higher. For the boiler to be economical, it needs to operate at a minimum of 60% of its rated power. Therefore, determining the correct boiler power is crucial for maximizing its efficiency over the years of use.
Of course, to somewhat plan the costs, you can make an approximate estimate of the required boiler power yourself. However, it is essential to consider that not everything depends on the square footage being heated. Energy losses, and therefore the required boiler power, greatly depend on the quality of insulation and the quality of the windows and doors. This is precisely why a professional assessment is invaluable.
A very rough estimate would be that a 15 kW boiler can heat an area of 1,615 square feet (150 square meters), while a 25 kW boiler can heat a house with a surface area of 2,690 square feet (250 square meters). This is a very rough estimate for an optimally insulated building and should be taken with a grain of salt, as much depends on the quality of insulation. Insulation quality can impact energy consumption for heating by up to 40%!