I've made getting my electric bill ever lower into something of a hobby. I live in Texas and air conditioning isn't optional here. People who have never spent a summer here tend to scoff and think we're all wimpy. They change their minds after a visit.
The first July we lived in our house our electric bill was $360.00. Last July it was $130.00.
The first thing I did was install platinum window film on all our South, East and West windows. It's a nice little DIY job and the payback is instant.
Switching to all CFL was next. People always talk about the electrical savings of the lights themselves, but incandescent lights put off an amazing amount of heat. If they aren't heating your indoor air then your A/C doesn't have to work against them. It's an indirect savings of electricity but I'll take it.
Next I installed a shade sail on our patio. If you install one make sure you use some heavy duty bungee cords to secure it. They can bounce around a good bit in any wind and will last a lot longer if all the stress isn't taken by the shade itself.
I never use my clothes dryer in the summer. The clothes actually dry faster on the clothes line and I don't have to pay to heat the dryer and then pay again to cool the house down from the dryer heat.
We installed a tankless water heater. It's electric because we don't have gas in my area but it still paid for itself within a year.
Finally, when the old A/C started to act up we installed a new high seer Heat Pump.
You can go here
http://www.cooltoday.com/blog/article/SEER-ac-energy-efficiency and check your savings. There are three different calculators so you can pick the one you like. If you have a 24 year old unit I'll bet that if you cough up the money for an efficient unit then your savings are going to be a heck of a lot more than $1200 over the life of the unit.
Do go with a higher seer rating as opposed to the cheapest unit you can get. You'll get your money back and be comfortable doing it.
I was amazed at the price differences when I was calling around getting installation quotes. In our area it really paid to make a lot of calls. We limped through the summer and got our unit installed between Thanksgiving and Christmas. It was a slow time for the company and I got an extra discount. The workers weren't about to die of heat exhaustion in my attic either so they took their time and did a good job.
The next thing on my list is installing a whole house fan. It's amazing how cool those things can keep a house if you buy the correct size. If you're going to be anywhere near the water then the temps will cool down at night and a whole house fan will let you take advantage of that.