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What Happens if My Furnace Is Not the Right Size for My House?


Furnaces are sized according to the square footage of the space they are expected to heat. If your home is smaller than average, the furnace you buy should be smaller than average. When the size is not based on the square footage of space, it’s usually determined by figuring out how many BTUs (British Thermal Units) the furnace can deliver.

While this is difficult for the average homeowner to figure out all by themselves, a professional HVAC company like Ideal Services Heating And Cooling has trained technicians that will do the calculations and get the best furnace size for your home or business.

Oversized Furnace

Oversized furnaces do not run long enough to bring the temperature in your house to a level that’s comfortable for you. This wastes energy because the furnace will turn on and off more frequently, which increases wear and tear on components such as blower motors and controls.

An oversized furnace can cause comfort problems that may only be rectified by installing a new system. That can be expensive. If you do need to change your furnace, buying the right size furnace will save you considerable money over time.

Undersized Furnace

Buying a furnace that is too small for your house can lead to poor heating, which in turn will cause you to use more energy. This wastes money and causes your monthly bills to go up.

Furnaces that are too small don’t run enough to keep your house warm at a comfortable level. This is a comfort issue and reduces your standard of living.

It may also lead to the following;

  • You have to turn the thermostat up higher than you prefer.
  • It wastes energy and money.
  • A space heater or fireplace may be needed in one or more rooms because they won’t heat up to a comfortable level.

Signs Your Furnace is Too Big

Oversized furnaces can cause problems.

  • Temperature Imbalance

You may notice that one or more rooms are too warm, while others are too cool.

  • Furnace Runs Constantly

If your furnace runs constantly, it could be too big for your house. It may turn on and off more frequently because it’s working harder than necessary to keep your home at a comfortable temperature.

  • Furnace Not As Efficient

An oversized furnace will use more energy to heat the same size space. This leads to higher energy bills.

  • Short Cycling

Look for constant cycling of your furnace because it’s a sign it’s too big for your home or business.

  • Moisture Problems

Moisture can build up in your home when too much air is drawn out to adequately heat it. You may notice condensation on windows or water dripping from the windowsills during rainy weather. The problem will only get worse as you turn up the dial on your furnace.

  • Blower Vibrations

Look for the blower motor vibrating on the floor or against your furnace’s casing.

  • High-Pitched Whine

A loud, high-pitched whine when the furnace kicks on is another sign of an oversized unit.

  • Difficult Installation

The furnace should fit easily in the space where it will be installed. If you have to make many adjustments to get it to fit, it’s probably too big for your house.

  • Excessive Noise

Excessive noise when the furnace is running could also signal that it’s oversized. You may have trouble sleeping or conversing in a room when the furnace is running.

  • High Energy Bills

A furnace that’s too big will cause your energy costs to be higher. Look for a sudden increase in your monthly bills.

Signs Your Furnace is Too Small

When your furnace is too small, you may experience these;

  • Temperature Problems

If the furnace is too small for your house, rooms may not heat up sufficiently. You’ll have to set the thermostat higher than usual to compensate for this.

  • Small Room Heat Loss

You may notice that you have to warm up one or more rooms in your house, even when the rest are comfortable.

  • Your Furnace is Always on

You may find that your furnace is always on with the thermostat set at a constant temperature. This means it’s working harder than necessary.

  • Your Home is Never Warm Enough

You may wear heavy clothing inside your home and still be cold. This happens because the furnace isn’t able to heat it properly.

  • Your Utility Bills Are Always High

You may have noticed a gradual increase in your monthly utility costs. This is because you’re using more energy than necessary to heat your home.

Contact Us If You Think Your Furnace is Not The Right Size For Your House

If you notice any of the symptoms described earlier, your furnace may be too large or small for your house. Give us a call to schedule an inspection and find out if it’s time to replace the unit , or schedule your service by calling us at (919) 283-3474 .