So you have an older AC unit. You live in the south where you run the air all the time. You are a perfect candidate for a Heat Recovery Unit.

What is it you ask? It is an add-on device that works with your Heat pump or air conditioner to make hot water. It uses the hot compressed refrigerate to do it. Instead of blasting the hot temperatures into  the atmosphere, it  puts it into the water.

Trevor-Martin Corporation makes a heat recovery unit. (They also make add-on heat pumps)

You can read the benefits for yourself but I would like to post just one thing,

I heard that Heat Recovery Units will decrease the efficiency of my air conditioning system. Is this true?
Absolutely not!! As a rule of thumb, a Heat Recovery Unite will increase your A/C efficiency by 10%. It also reduces the head pressure on the compressor; thereby reducing stress and improving compressor service life.
You get three benefits from adding a heat recovery: Free hot water for your house; reduced air conditioning cost; and improved A/C operating life.

Sounds very good to me. Since I don’t run the air for more then six months a year it does not make me a great candidate for it. But, if you do have a large cooling load, think of a restaurant or gas station with a car wash, your hot water would be… for the most part… free.