Heating System Goldilocks – Is Yours Too Big, Too Small or Just Right?
Do You Have The Right Size Heating System?
Most people don’t think about the size of their heating system. The equipment is just there, and is expected to keep their homes comfortable. But the size of the heating system – actually the volume of its heat energy, not its measurements – is the key to cost-effectively keeping your home at a comfortable temperature.
The default answer most homeowners give is that “bigger is better.” But that’s not always the case. Of course, a system that doesn’t produce enough heat is going to run longer to get your home to your preferred temperature. But if you have an oversized system, it will blast out heat, and make you uncomfortable by providing too much too quickly, and then shut off, only to cycle back on as the temperature drops. Every time the system cycles back on, it’s costing you more money. The trick is to have a heating system that’s properly sized, so that it can bring your home to the desired temperature, without scorching your lungs, and maintain the proper temperature evenly.
Time to sharpen that pencil, or pull out the calculator, because when it comes to right-sizing a heating system, there’s some math involved.
Let’s determine how much heat you need, first. A home in Florida is going to need a lot less warmth – and so a “smaller” furnace or boiler – than one up here in Massachusetts. The country is broken up into Climate Zones just for this reason – they take into consideration the differences in seasonal temperatures. Massachusetts is Zone 4, with an estimated need of 40-50 BTUs per square foot. Where you fall on that range is determined by how well insulated your home is. If your home is 2,200 square feet, you need a heating system that will output between 88,000 and 110,000 BTUs.
A BTU – or British Thermal Unit is the amount of heat necessary to raise 1 pound of water 1 degree Fahrenheit. Your boiler or furnace has a BTU input value, which refers to the energy consumed while it’s running. That’s the fuel you’re paying for! That number is probably somewhere between 50,000 and 120,000.
The AFUE (Annual Fuel Utilization Efficiency) number tells you just how efficient the furnace or boiler is. A unit with an AFUE of 80 is 80% efficient, and will output 80,000 BTUs from our 100,000 unit; an AFUE of 90 is 90% efficient and outputs 90,000; and an older system with an AFUE of 60 is only producing 60,000 BTUs of warmth for every 100,000 BTUs of fuel it burns through.
Let’s go back to our earlier furnace calculations. Remember, if you have a new, 2,200 sq. ft. home with good insulation, you need about 88,000 BTUs. That means you probably want to make sure you have a furnace or boiler rated at 100,000 BTU input with at least a 90% AFUE.
Before buying any new equipment, you want to talk to a heating professional who can properly assess your home’s needs, and review the options available to you. They will also be able to recommend other steps to take to increase your current system’s efficiency and your overall comfort.