I install a lot of high efficiency systems.
80% 16 SEER and above and 20% 15 SEER.

for example Bryant Evolution / Carrier Infinity systems:

There is a group of 15 of the best assemblers in the Bryant/Carrier plant that put these heatpumps/AC together. All other systems are built on a assembly line.
The parts used on the systems are top notch,
They are built better and they are more quiet.
These systems are data controlled systems so they communicate with each component to maximize the comfort level.

The compressors are 2 speed scroll compressors.

~ 3 Ton - 1 stage speed(low) runs about 5amps and high speed around 10amps. The system will run about 80% on low speed and will take out humidity with more precision.
Low speed cost around 15cts an hour to run.

After analyzing around 50 installs the average utility cost (heat pump) was $47 a month to run the air conditioning system in my area.

The thing is, if you are going to purchase a air conditioning system. Hopefully the contractors you choose will offer and explain to you these systems.
If they don't then they are not very good companies.
The should offer the best! Then see if they can fit it in your budget.

As a customer you want the best you can afford and should look into the top systems.

Hello: I have a Bryant, 288 18.3 SEER Heat pump that was
installed in the spring of 2009. a lot of the savings depends on the unit that you are replacing. In my case
the 10 + year old Bryant heat pump was a SEER 10 so my
Electric bill has decreased on average 60 dollars a month.
A better way to determine your saving is the Electric usage
over a year compared to an average of electric used in the past. Using solely the Utility bill can be misleading due to Utility costs rising.
But more importantly the comfort of your home will increase
dramatically both in the Summer and Winter, How do you identify savings for that ?
Another important aspect is to select a installing company that has a good record, check out a few individuals that have had the units installed, look at the workmanship, did they level the outside unit, did they replace the flex conduit, did they protect the cooling line with the black covering, does the system
work smoothly, become informed before you purchase so that
you can determine a good install from a bad one. When
I walk around my condo complex of 356 condos and see some of the installations, it is unbelievable yet the residents
don't seem to know or care and so in the future they will be unhappy with the performance.

running the numbers often I have found that performance,
savings & ROI are better for 15-17 SEER.
In my hot humid climate the higher dehumidification is with
15 to17 SEER ratings.
Most of my clients save 30% by upgrading to these efficiency units, just hvac savings alone.

as stated above..savings depend on what you start with
(8,10,11 Seer..) and what you upgrade to.
electrical rates also factor into savings.
but just the kwh usage, not additional fees.

best of luck

if heat pump and depending on location/climate, I would be more concerned about the AHRI HSPF efficiency for the system quoted.

I still believe 15 SEER and 12.50+ EER is about the sweetspot for AC efficiency and up front and operating cost. The jump to two stg and higher efficiency comes with a cost that may not have a reasonable payback.

IMO

what td said about the sweet spot.