Heat Pumps versus Central Air Conditioners
In this age of high energy costs and environmental awareness, choosing the right cooling system for our homes is a crucial decision. The two main options are air conditioning systems or heat pumps. Let's take a look at how they compare.
Heat pumps actually operate as both heating and cooling systems. In the cooling mode, they take heat from the internal air of the home and pump it to the outdoors. To produce heat, they collect it from air, water, or the ground outside and move it inside. Here's a simple way to describe what these units do: they move heat from one place to another. Both heat pumps in cooling mode and air conditioners use the Seasonal Energy Efficiency Rating (SEER), which tells how efficiently they use electricity. The higher the rating, the less power they consume. Heat pumps must now have a SEER of at least 13. A higher SEER is desirable in a warm climate because of the need to more frequently provide cool air to the home. Heat pumps also are rated according to the Heating Seasonal Performance Factor (HSPF), which refers to the power used when the unit is in heating mode. Because a heat pump's coils are outside, they become ice collectors during the winter. Heat pumps use burners to melt the ice and push warm air into the house. In colder climates, this increases the operating costs.
Air conditioners manufacture cool air by evaporating Freon or some other refrigerant product. Basically there are coils both inside (for cold air) and outside (for warm air). The units contain a compressor to change Freon into hot, high-pressure gas that travels through the coils. As it does so, it loses its heat and becomes liquid; the liquid in turn goes through a valve and evaporates into cold, low-pressure gas. When it enters the coils, it absorbs the indoor heat and lowers the temperature. Residential air conditioners also use the SEER as a measure of their efficiency. (Larger commercial units often measure energy efficiency by the Energy Efficiency Ratio (EER). This measure shows the number of British Thermal Units (BTU) of cold air provided for each watt of electricity. When talking about cooling units, 1 ton is equal to 12,000 BTU. To find the EER of an air conditioner, divide the BTU rating by the wattage. For example, let's say that a 12,000 BTU air conditioner uses 1600 watts to run -- then its EER (12,000 divided by 1600) is 7.5. The higher the EER, the more efficient the air conditioner, so a higher EER is more desirable. The drawback is that more efficient units are more expensive.