Right-size Your Cooling and Heating System by Calculating Efficiency

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Energy Efficiency
Half of the utility costs in the average American home go to cooling and heating, making climate control the single biggest expense in most U.S. homes.

Half of the utility costs in the average American home go to cooling and heating, making climate control the single biggest expense in most U.S. homes. Calculating efficiency for a home's cooling and heating system is the key to conserving resources, lowering bills and making an investment that improves the home's overall cost and comfort.

Measuring the Efficiency of Heating Systems

  • Furnaces, which heat air that is then distributed around the home through a network of ducts, can operate with an efficiency of as little as 59 percent or as much as 98.5 percent, depending on the unit's age. Furnaces are expected to last between 15 and 30 years.
  • Boilers, which heat water to provide either steam or hot-water heat to radiators, pipes or coils, vary between 50 and 90 percent efficiency, depending on their age and the type of fuel they burn. Like furnaces, boilers last 15-30 years.
  • Electric heat is very efficient, between 95 and 100 percent. But space heaters and baseboard units come with drawbacks such as specific location requirements and difficulty with zone control.
  • Ductless heat pumps require more of an upfront investment, but they are the most efficient and provide the most precise zone control. They don't require invasive ductwork and they don't burn physical fuel.

Calculating Efficiency for Different Types of Cooling Systems

Two-thirds of American homes have mechanical air conditioning. Homeowners spend $11 billion each year to run their air conditioners, which fall into three main categories. Here is how to measure the level of efficiency of each air conditioning system.

  • Window-mounted units are the most popular option. They're relatively cheap to purchase and run, but they're horribly inefficient. If a home has a window unit without correctly installed foam panels between the window frame and the air conditioner, it is almost certainly losing air through leakage — as much as 10 percent.
  • Central air can be cost effective, but only as long as the system's ductwork remains well maintained and doesn't run through unconditioned rooms such as garages. The outside compressor unit must be kept clear of leaves, snow and other debris to run at peak efficiency.
  • Split-ductless units come with a higher up-front cost, but don't lose any energy through ductwork. They retain their efficiency in every climate and are low maintenance.

Cooling and heating dominates the utility budgets of most homes. Each type system comes with pros and cons, but calculating efficiency is crucial to choosing the system that will provide the most comfort, the most control, the best use of resources and the greatest cost savings.


While the upfront cost of a whole-home or multi-room ductless system may be higher than some of the alternatives, the long-term savings will offset the cost over the lifetime of the system. Cooling and heating costs can be minimized by offseting furnaces and central air systems with a ductless solution, reducing monthly expenses by taking advantage of ductless' efficiency over traditional options.

This article and its content are sponsored by Mitsubishi Electric US Inc., Cooling & Heating Division.

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