Residential air conditioning comes with its own set of terms just like the heating side.
Size also matters in air conditioners. Too small and it will not cool your home properly and too large and it can freeze up because the ducting and air flow are insufficient. Either extreme leads to hot conditions and unhappy people; neither are preferred.
Air conditioners are measured in tons of cooling (one ton of cooling is 12K BTUs) and in efficiency ratings notated by a SEER (Seasonal Energy Efficiency Ratio) number from 13 to more than 30. A higher SEER number means the air conditioner requires less energy to run.
- A lower efficiency unit costs less up front but has a higher monthly cost.
- A high efficiency unit costs more up front and then has a lower monthly cost.
- A 24 SEER unit is about 2.5x the cost of a 13 SEER unit.
When looking at total cost of ownership the break even point for Northern Utah is about 16-18 SEER. An air conditioner runs less here than a furnace and so the return on investment of a more expensive unit takes longer to realize.
One amazing and oft overlooked component to cooling is a whole-house fan. These are used whenever the outside air temperature is less that the inside temperature, usually in the evening and nighttime. Whole-house fans move inside air out through the attic, this cools the attic at night and a cooler attic means a cooler home. One example is a home in Kaysville (look for this educational video). They cool their entire home (and attic) to the outside temperature each night, frequently down to 65 degrees in the summertime. Their whole-house fan costs 7 cents per hour to operate and they saved $120 just in August. A whole-house fan pays for itself in about two years. ERS does not install these but we will refer you to a couple different trusted installers for you to pick from.
Attic insulation is another major factor and it prevents the heat in the attic from transferring into your living space.