Furnaces have different efficiency ratings which are indicated as a percentage. The higher the percentage, the more efficient the unit. Higher efficiency furnaces produce the same amount of heat as lower efficiency units of the same output BTU size. The difference is that the higher efficiency furnaces use less gas to do so, thereby saving you money.
80% efficiency is the lowest BTU rating of furnace offered by most manufacturers nowadays, although it is still significantly higher than older furnace efficiencies which are sometimes as low as 60%.
We have multiple types of efficiency furnaces for you to select, 80% efficient and 93% efficient and 95%+ efficient. Which efficiency unit you decide to install is up to you. Just remember that the higher the efficiency the lower the cost to run it.
The heating capacity of a furnace, also referred to as size, is measured in thousands of BTUs (British Thermal Units). Furnaces are rated by the input BTU’s, that is, the amount of fuel energy that goes into it when running. Different furnaces of the same input BTUs will have different output BTUs if the furnace efficiency ratings are different. Select a furnace for your home according to the output BTUs, as this is the actual heating capability of the furnace. You can easily calculate the output BTUs of a furnace according to the efficiency rating of the unit and the input BTUs – simply multiply the efficiency percentage by the input BTUs. For example, a 100,000 BTU furnace at 80% efficiency will produce 80,000 BTUs of heat output, whereas as 100,000 BTU furnace at 92% efficiency will produce 92,000 BTUs of heat output.
There is only one correct size furnace for your home. You don’t want a unit that is too big, as it will turn on and off too frequently, be inefficient, and accumulate moisture in the heat exchanger which can damage the unit over time. And you don’t want a unit that is too small as it won’t properly heat the home. You want just the right size. How do you determine which one is just right? There are several ways you might go about determining the correct furnace heating capacity (or size) unit.
If you are replacing an existing furnace, look at what size you have. If the unit you have now is the correct size for your home, replace it with the same size. How do you know what size you currently have? Look at the name plate on the furnace usually located somewhere inside the unit (remove service panel to find). Remember, furnaces are rated by input BTUs, but you will want to determine what the actual output BTU is (often also listed on name plate) when selecting the right size replacement unit. We recommend that you still have it measured out. In some cases you can move to a smaller BTU output if the windows have been changed or more insulation has been added. We do free estimates.