Central air conditioning unit outside of a house
Christian Delbert/Shutterstock.com

When the thermometer gets into the 80s and higher, nothing feels better than staying inside a cool, quiet house with central air conditioning.

But how much does it cost to install central air? While the average cost is around $5,000, the price can range from as little as $2,800 to more than $10,000, according to a survey of Angie’s List members.

The exact cost for your house depends on a number of factors, including the type of system you buy and whether your house has ductwork. To get a better idea how much this upgrade will cost—and how to do it right—consider these factors:

What type of central air system should you choose?

There are two main types of central air conditioning systems: the split system and the packaged unit. Both work in the same way, using the expansion of refrigerant to cool a coil, which in turn cools the air that passes over it. But the two systems differ in the way they are set up.

The split system, which is the most common, features a condenser outside the home and a fan-and-coil system inside, with the two units connected by pipes that transfer the refrigerant. The packaged air conditioner contains both components integrated into one, and is generally used when there isn’t enough space for a split unit. Packaged units are often installed on the roof, making the installation cost greater.

If you have a forced-air furnace, the split system is the least expensive, since the cooling system is fitted into the air handler of your furnace. If you don’t have forced air, your house will have to be retro-fitted with ductwork. This could double both the time and cost to install central air.

Looking to install central air? A personal loan or a HELOC are great ways to pay for it.

How much central air conditioning do you need?

An air conditioner’s size is typically referred to in terms of its tonnage. That’s not the unit’s weight, but its cooling capacity. One ton of cooling is about how much cooling you’d get by melting a ton of ice.

To determine the size cooling unit you need, your contractor should use the Air Conditioning Contractors of America Manual J, which takes into account many features of your house, including its windows, insulation and orientation to the sun. Don’t hire a contractor who simply sizes your unit by the square footage of your house.

As many as half of home air conditioners don’t work as well as they should, because contractors size them at least half a ton larger than necessary. That’s money down the drain for you, because a too-large unit costs more to run and will cool a room too quickly to remove the humidity.

Your ongoing energy costs

Besides the installation cost, you’ll want to consider the ongoing cost of running your new system. The good news is that besides being out of the way and quiet, central air conditioners are more efficient than window units. Even if you’re replacing an existing central air conditioning unit, you’ll end up saving 20 percent to 40 percent on energy costs with a new system.

To make sure you get the most efficient unit, look for an “Energy Star” label, a government-backed label awarded to qualified products that are generally 15 percent more efficient than standard models. Central air conditioners also receive a SEER rating, which stands for seasonal energy efficiency ratio. The higher the SEER number, the better a system is for the environment and the lower your energy bills are likely to be.

Learn more about home improvement loans at Bankrate.