How to Properly Size a Heating System

We’ve all heard the phrase bigger is better, but it isn’t always true with heating equipment. An oversized heating system may keep your home warm but it won’t necessarily make it comfortable, as it’s more prone to temperature swings. It’ll blast out heat and provide too much too quickly, shut off, then cycle back on again once the temperature drops. As this process repeats, the temperature will fluctuate and, because it’s inefficient, cost you money. On the other hand, an undersized heating system won’t provide enough heat to keep you warm. How do you find the right size? What factors do you have to account for?



Heating equipment is measured in British Thermal Units (BTUs) – or, the amount of energy needed to raise a pound of water by one degree Fahrenheit. The boiler or furnace in your home has a BTU input value, or how much energy it consumes when it’s running. There’s no one-size-fits all heating system because every home is different, however, typically BTU input values range between 50,000 and 120,000.



Living in Massachusetts, you’ll need more warmth than you would in California. The country is divided into different climate zones that take into account seasonal temperature differences, and Massachusetts is in Zone 4, which requires 45-50 BTUs per square foot.



Each boiler or furnace has an Annual Fuel Utilization Efficiency (AFUE) rating, which measures how efficiently the equipment converts the energy in its fuel to useful heat over the length of a year. A boiler or furnace with a 95 AFUE rating, for example, converts 95 percent of the energy in its fuel to heat for the home, while 5 percent finds its way out through the walls, doors, chimney and elsewhere. A boiler or furnace with a 95 AFUE rating outputs 95,000 BTUs from a 100,000 BTU unit.


Doing the Math

Suppose you have a 2,000-square-foot home. Living in Massachusetts, you need around 45 BTUs per square foot. By multiplying the square footage of your home by the BTUs per square foot needed, you’d wind up with an output of 90,000 BTUs. If your system is 95 percent efficient, you’ll probably want a boiler or furnace around 95,000 BTUs.


Contact Fsi Oil and Propane

Insulation levels, window location, air infiltration rates, homeowner preferences, and the efficiency of home appliances also play a role in calculating the right size heating system for your home, so don’t leave anything to chance. Talk to a professional who can assess every factor and pinpoint the heating needs of your home and review available options with you. Contact Fsi Oil and Propane today.