Why Is The Coefficient Of Performance A Critical Consideration For Heat Pumps?
If you're looking at installing new HVAC systems, you might find your head spinning as you deal with an onslaught of terminology and acronyms. Do you know your SEERs from your AFUEs? If not, then adding another piece of jargon to the mix might not sound like much fun. Fortunately, coefficient of performance (COP) isn't hard to understand, and it's critical when choosing a heat pump.
Unlike other heating systems, heat pumps don't work by converting stored energy into heat. Instead, a heat pump moves energy from one place to another. Air conditioners work the same way, which is why some people refer to heat pumps as reversible air conditioners. However, this design requires viewing their efficiency differently from other heating systems.
How Does Efficiency Differ From Furnaces?
When considering a furnace, you usually look at a value known as the annual fuel utilization efficiency (AFUE). This straightforward rating tells you the percentage of burned fuel converted to heating energy for your home, with the rest of the fuel escaping as waste heat. A higher AFUE means more utility costs go directly into keeping your home warm.
Since a heat pump doesn't burn fuel to create heat, you can't use a similar method to judge its efficiency. Instead, the coefficient of performance (COP) tells you the energy your system consumes to move an equivalent amount of energy. If your heat pump can deliver an average COP of three, that means it can move about 3000 watts of energy for every 1000 watts you put into the system.
Note that heat pumps may have different COP values for heating and cooling mode, with many pumps delivering more efficient operation while heating. Additionally, some heat pumps may use a seasonal coefficient of performance (SCOP). SCOP values work just like COP values, except they attempt to account for changes in load throughout a season.
How Should COP Factor Into Your Purchasing Decision?
COP may seem like an abstract concept, but it's relatively comparable to other efficiency measures. Generally, you can think of a heat pump's COP as its efficiency above and beyond traditional heaters. For example, an electric heater has an AFUE of 100%, equivalent to a COP of 1.0. In other words, you can get as much energy out of an electric furnace as you put into it.
Since heat pumps move energy, you get more heat from the system than the amount you put in. As a result, heat pumps always have a COP above 1.0. While a heat pump is always the most efficient option, it's not always the most cost-effective one. You'll also need to consider your local energy costs and how electricity compares to other options, such as natural gas or heating oil.
Fortunately, COP provides an excellent tool for making these comparisons, and SCOP can provide an even more accurate energy usage estimate. By looking at your heat pump's COP, you can determine how much more efficient it is than a traditional gas or oil furnace. You can then use this information to compare fuel costs to electricity costs, helping you determine if a heat pump will save you money.
For more information, contact a heating contractor near you.