The most important thing to consider when replacing your furnace is to make sure the furnace is the correct size for your home. If the furnace is too large the house heats quickly, too quickly, then turns off. If the furnace is to small it will not keep the house warm enough when the weather is cold.

When we recommend a replacement furnace we conduct a heat loss calculation called a Manual J Calculation to size your furnace and cooling product recommendation.

US Department of Energy

Manual J and Manual D: The Correct Way to Size a System

Correct system sizing requires considering many factors other than simply reading the nameplate of the existing unit. Key factors for correctly sizing a heating and cooling system include the following:

The local climate
Size, shape, and orientation of the house
Insulation levels
Window area, location, and type
Air infiltration rates
The number and ages of occupants
Occupant comfort preferences
The types and efficiencies of lights and major home appliances (which give off heat).
Homeowners should insist that contractors use a correct sizing calculation before signing a contract. This service is often offered at little or no cost to homeowners by gas and electric utilities, major heating equipment manufacturers, and conscientious heating and air conditioning contractors.

The biggest mistake people make during the hottest days of summer is to run their air conditioner during the day and then open their windows at night. Part of the work an air conditioner does is to remove humidity from the air – moisture. The moisture in the air increases at night because generally the night air is cooler.  If you open your windows at night the next day the air conditioner has to work harder to remove the humidity. Opening windows at night when you are running an air conditioner during the day will reduce your energy efficiency causing higher utility bills.

A maze of heating and air conditioning ducts runs inside the walls and floors of 80 percent of American homes. As the supply ducts blow air into the rooms, return ducts inhale airborne dust and suck it back into the blower. Add moisture to this mixture and you’ve got a breeding ground for allergy-inducing molds, mites and bacteria. Many filters commonly used today can’t keep dust and debris from streaming into the air and over time sizable accumulations can form — think dust bunnies, but bigger.

To find out if your ducts need cleaning, pull off some supply and return registers and take a look.

If a new furnace is being installed, you should probably invest in a duct cleaning at the same time, because chances are the new blower will be more powerful than the old one and will stir up a lot of dust.

Professional duct cleaners tout such benefits as cleaner indoor air, longer equipment life and lower energy costs. Clean HVAC systems can also perform more efficiently, which may decrease energy costs, and last longer, reducing the need for costly replacement or repairs. Cleaning has little effect on air quality, primarily because most indoor dust drifts in from the outdoors. But it does get rid of the stuff that mold and bacteria grow on, and that means less of it gets airborne, a boon to allergy sufferers.

With the proper attention, heating and cooling systems can keep you comfortable year-round. Heat pumps and oil-fired furnaces and boilers need a yearly professional tune-up. Gas-fired equipment, on the other hand, burns cleaner and can be serviced every other year. A close inspection will uncover leaks, soot, rust, rot, corroded electrical contacts and frayed wires. In furnace (forced-air) and boiler (hot-water) systems, the inspection should also cover the chimney, ductwork or pipes, dampers or valves, blower or pump, registers or radiators, the fuel line and the gas meter or oil tank — as well as every part of the furnace or boiler itself.

Next, the system should be run through a full heating cycle to ensure that it has plenty of combustion air and chimney draft. Finally, cleaning the burner and heat exchanger to remove soot and other gunk will prevent such buildup from impeding smooth operation. For the burner, efficiency hinges on adjusting the flame to the right size and color, adjusting the flow of gas or changing the fuel filter in an oil-fired system. A check of the heat pump should include an inspection of the compressor, fan, indoor and outdoor coils and refrigerant lines. Indoor and outdoor coils should be cleaned, and the refrigerant pressure should be checked.

You may wish to consider replacing your air conditioning or heating system if it is old, inefficient or in need of repair. Today’s systems are as much as 60% more efficient than those systems manufactured as little as ten years ago. In addition, if not properly maintained, wear and tear on a system can reduce the efficiency of the system.

If you are concerned about energy savings or are faced with an expensive repair, you may want to consider replacing your system rather than enduring another costly season or paying to replace an expensive component.

The energy cost savings of a new unit may provide an attractive return on your investment. If you plan on financing the purchase, the monthly savings on your utility bill should be considered when determining the actual monthly cost of replacing a system. The offsetting savings may permit you to purchase a more efficient system.