When you go to install a furnace, size will be important. After all, you need to make sure that you purchase a home furnace that’ll offer everything you need. A home furnace can be an extremely expensive purchase, and the wrong one will be hard to replace. That’s why calculating the correct furnace size for your home is so important. The right furnace will be more efficient, cost effective, and need fewer repairs.

It can be tempting to think that the right furnace size is the biggest one, but that’s not usually true. A furnace that’s too large for your home will short cycle. That means it’s turning on and off very frequently. This is bad for the furnace, since it creates condensation that can end up damaging it. Furnaces that are too small will run too long, and will be generally inefficient. They won’t last as long as you need them to, and will even shorten the lifespan of the furnace you buy. In the very coldest periods, a furnace that’s too small won’t do its job, and your home may feel cold.

So how do you decide on the right furnace size for you? When you go shopping, there are two ratings to look at. One is the input rating, and the other is the output rating. Both are calculated in BTUs, or British Thermal Units, in the United States. This measures the amount of energy the furnace uses while it’s running. The input rating tells us how much energy is used overall. The output rating tells us how efficient the unit is.

This means that a hundred thousand BTU furnace that’s very efficient would have around a ninety-two percent efficiency rating, or an output rating of ninety-two thousand BTUs. Be sure to look at the efficiency and the output, since they affect how much you spend and how much of your fuel goes out the exhaust vent without heating your home.

The standard method for determining furnace size takes into account your insulation level, which way the house faces, and how large your home is. It’s a little complex to do manually, but there are plenty of furnace size calculators online that can help you do it. It’s remarkably easy. Of course, if you don’t have the information to fill out the calculator, and don’t feel comfortable taking your best guess, you can always call in a pro. Professional furnace dealers or heating contractors can easily estimate your furnace size, and will often refund your fee if you end up buying from them.