Which Boiler Should You Choose According to the Size of Your Home?

How to choose the power of your boiler? 

The first thing you need to know is that the power of a gas boiler is expressed in kilowatts (kW) and corresponds to the energy produced by your equipment. This should not be confused with your actual gas consumption which is also expressed in kW. The different boiler models vary based on their power, making it easy to find the right one for your needs. If you choose a boiler that is too weak it may go into overdrive. The result? Your energy bill will be undoubtedly high, your hot water taps will have a weak flow and your radiators will be almost lukewarm. To avoid these problems, here’s what you need to know before choosing your boiler. 

Important details:

Before you rush out to buy a boiler, remember to consider all these factors: 

• The size of your home, including the ceiling height. 
• The insulation in your home, whether it’s good or poor.
• The number of occupants, to establish the domestic hot water requirements. 
• The region where you live, to determine the outdoor temperature index (OTI).
• The ideal temperature for heating the rooms in your home (we highly recommend the connected thermostat to regulate and automate the temperature in your home). 
• The possible use of other heating methods (electric, solar, stove etc.). 
• The use of your boiler, will it be used for heating and hot water or only for heating. There are several boiler options suitable for this purpose, such as condensing boilers, wood boilers, oil boilers, electric boilers, etc. 

The importance of your gas supplier:

When choosing your boiler, don’t overlook the choice of your natural gas supplier. If you’re in the middle of moving house, this could be the perfect time to switch suppliers. This makes it much easier for you to save money while still being able to enjoy the comfort of your boiler. To find an offer that suits your needs and budget, you can use an comparison site for energy suppliers. As soon as you have chosen your boiler and energy supplier, don’t forget to open your electricity and gas meter: it’s much more convenient! 

Easily calculate the kW required to heat a house  

If you are comfortable with numbers, you can always do the calculation yourself. To do this, you must use the following formula: Power = C x (DT + OTI) x V x DP.

Are you confused? Don’t panic, here are all the explanations: 

The C is the energy consumption coefficient (2 for a poorly insulated house, 1.6 for a well-insulated house). 

The DT represents the desired temperature, i.e. the average temperature you want to heat your home up to.

The OTI is the outdoor temperature index (15 in the mountains, 12 in the North, 7 in the South and 9 in the Centre of France).

The V corresponds to the volume to be heated and is obtained by multiplying the surface area of the dwelling and the height of the ceilings. 

The EL refers to the energy losses, you can assume a typical average of 1.3. 

 What boiler capacity is best for 150m²? 

Has calculus scared you away? You can’t understand anything anymore? To help you see it more clearly, here is an example for a 150m² house.  Let’s say it is located in the North, with good insulation, a standard ceiling height (i.e. 2.5 metres) and a desired temperature of 20°C: you would need a 25 kW boiler. 

This is a minimum, of course. If it is also used to produce domestic hot water, the output of the boiler may vary. In this case, you will need to add 10 kW for a large family, or 5 kW for a couple without children: a boiler between 30 and 35 kW will therefore be ideal. However, bear in mind that a single-storey house of 150m² will not need the same power as a multi-storey house.