The dog days of summer are here. So too are your dreams of having central air. Here's what you need to know about how much it costs to get it installed.

Size of your house

The bigger your house, the bigger the system you will need to cool your home. But that doesn't mean bigger is always better. You want an air conditioning system that is the correct size for your home. If the system is too large it will cycle on and off all the time, wasting energy and being loud and disruptive. If it's too small it will run constantly and will not effectively cool your house.

Do you already have a central heating system?

Many central air conditioning systems use the blower that is part of the furnace to distribute cool air through your home. If you do not have a central heating system installed, it is most cost effective to install both heat and air conditioning at the same time. If you already have central heat you can use the existing fans and duct system for central air.

Do you need duct work?

Although most newer homes have ducts and vents already in place through the heating system, many older homes have old convection heating system or even baseboard heat and have no ductwork. If this is the case, you will need to install ducts and cut and install vents. This is an extensive and costly job. If you need to install ductwork and vents, this would be the time to explore upgrading the heating and cooling systems at the same time, as both will be much cheaper when done together than if done separately.

How's the insulation in your home?

If your home is well built and well insulated, then both your heating and cooling systems will work more efficiently, and therefore more cost effectively. If you have a brand new central air conditioning system, but poor insulation, you will spend considerable more on your energy bills than you need to. It would be worth exploring an upgrade to you home's insulation if this is the case.