How to Size Home Boilers

Calculate the square footage in your home per floor by measuring the height and width of each room with a tape measure. Multiply the height and width together with a calculator to get the square footage of the room. Add the rooms together for each floor.

Calculate the average temperatures during the winter in your area, which can be found online. This gives you an idea of how cold it gets and how much heat you need in the coldest moments.

Examine the types of appliances in your home and how efficient they are. Appliances give off heat and therefore could affect how much additional heat you need in your home.

Count the number of windows in your home and measure the size. Estimate how efficient each window is at retaining heat. Examine the insulation in your house and write down the insulation rating, which should be marked on the insulation wrapping if you can still locate it.

Fill out an online boiler size calculator as an additional tool. Print out the results after entering the data about your home's square footage and insulation.

Consult with a heating professional using your figures and data to get an opinion on the boiler size needed. Consultations are often free of charge. Getting two or three different opinions using your data gives you an effective estimate on how large your boiler should be. This is a somewhat subjective estimate and not an exact science.