# How to choose the power of the boiler How to choose the power of the boiler: the calculations and evaluations to be made to choose the appropriate power of the boiler for domestic heating.

In the articleHow to calculate the thermal powerwe have provided you with the tools to best choose the power of a heating system (air conditioning, air conditioner, heat pump ...), in this article, we will talk specifically about oneboiler and how to choose thepowermore suited to domestic needs.

• How to choose the power of the boiler, the heat requirement

Forchoose the power of the boileror any heating system, the first thing to do is to determine the heat requirement of the building to be heated.

The exact calculation of the maximum heat requirement should take into account several factors, such as the thermal transmittance the materials used for the construction of the building (type of fixtures, solar shading, thermal plaster, insulating panels, presence of any thermal coat ...) an approximate calculation of theheat requirementit is possible through a simple formula that uses only the living area to be heated. The formula sees.

Heat requirement = boiler power in kW =
surface to be heated (in meters) x specific heat requirement (kW / m²).

The specific heat requirement is an approximate value that is fixed at 0.05 kW / m² but each of you can use a value as close as possible to your thermal needs:

• a house with very low requirements, therefore with excellent insulation, can use an approximate value of 0.03 kW / m²
• Houses with good thermal insulation can use an approximate value of 0.05 kW / m² for the calculation of the heat requirement
• houses with fair thermal insulation can use an approximate value of 0.08 kW / m²
• homes with dated masonry, without particular thermal insulation, can use an approximate value of 0.12 kW / m²

The first thing to do forchoose the power of the boileris to calculate the heat requirement.

Starting from a 75 m² apartment with a ceiling height of 2.70 m, the m³ are calculated by simply multiplying:

• 75 m2 x 2.70 m = 202.5 m³

At this point it will be necessary to multiply the volume of the house just calculated by one of the coefficients seen above, obviously those who have a house built in the Eighties will have to apply the maximum value equal to 0.12 kW / m².

As is clear, the more insulated a house is, the lower the cost of buying the boiler and supporting it in energy terms.